LiveSync: Rename agents to backends
LiveSync: Rename agent.py to backend.py
Add run-tests to run all unit tests

We need to run it from the correct folder containing pytest.ini in
case the tests need certain indico plugins.
LiveSync: Remove debug print statements
Use new signal namespaces
Chat: Add info message if the table has no rows
Chat: Improve chat details layout in event page
Use form fieldset.

Fixes #2