Fix MainDb tester: it was creating tests accounts for nothing, which takes time and randomize the performance measurements made on the chatroom db loading.

Add RFC4028 support
Complete the tests
Remove a test in call_single_tester
Complete liblinphonecore to allow configuration handling from config files

Move license to GPLv3, update version number to 4.3.0.

Fix crash in maindb tester, and relax wait time in group chat suites because with --parallel mode there were sometimes exceeded.

This reverts commit 1d0495f8.

  - return nullptr if conference factory uri is not set
  - Address object is now more robust
  - remove custom SharedFromThis object
  - CoreAccessor throw exception if core is destroyed
  - Core must be created with a static method
  - Partial fetch of chat message
  - ...