* added support for multiple attachments to signal_messenger integration
* updated pysignalclirestapi version in requirements_all.txt
* reworked multiple attachments feature in signal_messenger integration
* stay backwards compatible by both allowing the "attachment" and
the "attachments" attribute.
* reworked multiple attachments feature in signal_messenger integration
* stay backwards compatible by both allowing the "attachment" and
the "attachments" attribute.
* small change in signal_messenger integration
* added deprecation warning for 'attachment' attribute
* small changes in signal_messenger integration
* use 'warning' instead of 'warn' when logging the warning message
* re-generated requirements_test_pre_commit.txt
* added tests for signal_messenger integration
* regenerated requirements_test_all.txt for signal_messenger integration
* added more signal_messenger tests
* remove signal_messenger integration files from .coveragerc
Paulus Schoutsen
Bernhard B