Bug #708628 - Add support for EmptyFolder operation
Bug #708121 - Add functionalities to help the addition of the low level tests for EwsConnection

- Add e_ews_folder_id_is_equal()
- Add e_ews_debug_get_log_level()
- Add EWS_DEBUG=3 debug level, which should only be used to log trace for the tests files
- Don't use streaming-based messages when we are logging