[configuration/addons.md] Initial commit (Moved from deprecated addons page) (#715)

* Moved addons installation article to a new page and edited headline hierarchy.

Signed-off-by: Jerome Luckenbach <github@luckenba.ch>

* s/{{base}}/\/docs/g

Signed-off-by: Jerome Luckenbach <github@luckenba.ch>

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Signed-off-by: Jerome Luckenbach <github@luckenba.ch>

configuration/addons.md

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+---
+layout: documentation
+---
+
+{% include base.html %}
+
+# Installation of Add-ons
+
+Depending on the [package](/docs/configuration/packages.html) you have choosen during your first time setup, there are already some pre-installed add-ons.
+Additional add-ons can be installed in the different ways, described below.
+
+## Through Paper UI
+
+Navigate to the add-ons section.
+Search for the desired add-on in the categories and press install.
+
+![installing Add-ons through Paper UI](./images/addons_index_installation_paperui.gif)
+
+## Through Configuration Files
+
+For this installation option you need to know the `id` of the desired add-on, e.g., network or mqtt1.
+
+You can find it out with the following command within [openHAB console](/docs/administration/console.html):
+
+```sh
+feature:list | grep ^openhab
+```
+
+A list of all available add-ons starting with "openhab" will be returned.
+It could look similar to this example:
+
+```text
+...
+openhab-transformation-xslt               | 0.9.0.SNAPSHOT   |          | Uninstalled | openhab-aggregate-xml   | XSLT Transformation
+openhab-voice-mactts                      | 0.9.0.SNAPSHOT   |          | Uninstalled | openhab-aggregate-xml   | macOS Text-to-Speech
+openhab-binding-amazondashbutton          | 2.0.0.SNAPSHOT   |          | Uninstalled | openhab-aggregate-xml   | Amazon Dash Button Binding
+openhab-binding-astro                     | 2.0.0.SNAPSHOT   |          | Uninstalled | openhab-aggregate-xml   | Astro Binding
+openhab-binding-autelis                   | 2.0.0.SNAPSHOT   |          | Uninstalled | openhab-aggregate-xml   | Autelis Binding
+openhab-binding-avmfritz                  | 2.0.0.SNAPSHOT   |          | Uninstalled | openhab-aggregate-xml   | AVM Fritz!Box Binding
+...
+openhab-binding-network                   │ 2.2.0            │          │ Uninstalled │ openhab-addons-2.2.0    │ Network Binding
+...
+```
+
+According to the [naming convention for bundles](/docs/administration/bundles.html#naming-convention-for-bundles) the *id* for the shown example is *network*.
+
+Another way to find the correct `id` is to look at the URL of the add-on documentation page.
+For example the url for the [mqtt Binding documentation](/docs/addons/bindings/mqtt1/readme.html) is
+
+```text
+https://docs.openhab.org/addons/bindings/mqtt1/readme.html
+```
+
+In this case, the `id` would be "mqtt1".
+Did you notice the trailing *1* in this id?
+This is because the mqtt Binding is a 1.x add-on.
+
+The trailing `1` has to be appended for `binding`- and `misc`-addons.
+It is *not needed* for other addon types like `persistence`.
+
+With this information we can now edit the *addons.cfg* file in the `config/services` folder on the machine you are running openHAB on.
+The path is depending on your installation.
+You can find out the correct locations on the corresponding documentation pages, e.g. [Linux](/docs/installation/linux.html#file-locations) or [Windows](/docs/installation/windows.html#file-locations).
+
+The file could look like this (depending on your choosen package and already installed add-ons):
+
+```text
+package = standard
+ui = basic,paper,habpanel
+action = pushover
+binding = astro,mqtt1
+transformation = jsonpath
+persistence = influxdb
+misc = restdocs
+```
+
+To install the network Binding like we want in this example, we just need to add the id *network* to the Binding section.
+
+```text
+binding = astro,mqtt1,network
+```
+
+After saving the file, the add-on will be installed.
+
+
+## Through manually provided add-ons
+
+> Attention:
+> This option is adressed to advanced users.
+> Installing add-os with a `.jar`file can lead to problems, because add-on dependencies may not be installed.
+> Please make sure to use this option only in special cases (like add-on testing for an upcoming version) or when you know what you are doing.
+
+For this installation option you need a bundles `.jar` file.
+One way of retrieving those files is mentiones above in the openHAB console part.
+
+Place the `.jar` file in the `add-ons` folder on the machine you are running openHAB on.
+As described already for the addons.cfg option, the path is depending on your installation.
+Place the .jar file in the folder Additional add-on files as described in File Locations ([Linux](/docs/installation/linux.html#file-locations), [Windows](/docs/installation/windows.html#file-locations) or [macOS](/docs/installation/macosx.html#file-locations)).