### Description
Now that we are delegating the help text to `device_managment.py`,
it should print out help as if it's invoked with `mbed device-management`.
This PR changes the argument parser and the help text to do just that.
### Pull request type
[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change
Developer API keys don't have the privileges required to get information about their owners. To correct for this, remove user name reporting and use the API key `owner_id` directly.
Fixes: IOTAUTH-1686
### Description
`mbed dm` will now accept the Pelion Device Management API Key and
Host on the command line with the following switches:
* `-a`, `--api-key` accepts the API Key
* `-S` (note capitol), `--server-address` accepts the Host
This is consistant with manifest tool parameters
Resolves https://github.com/ARMmbed/mbed-cli/issues/745
### Pull request type
[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change
Martin Kojtal
Cruz Monrreal
Jimmy Brisson
Brendan Moran
Jimmy Brisson