Use dict config for logging.

- Allow user to include a logging_config.py in the gajim user dir
- Support --logging-config to allow user to pass a custom logging config
- provide a default logging configuration: 'logging_config.py'
5 jobs for logging-improvements-20181031 in 4 minutes and 58 seconds (queued for 53 minutes and 11 seconds)
Status Job ID Name Coverage
  Test
passed #7934
run-appdata

00:00:07

passed #7932
run-mypy

00:00:26

failed #7933
run-pylint

00:04:09

passed #7931
run-test

00:00:15

 
  Build
skipped #7935
run-build
 
Name Stage Failure
failed
run-pylint Test There is an unknown failure, please try again
************* Module gajim.common.configpaths
gajim/common/configpaths.py:207:49: C0326: Exactly one space required after comma
('LOG_DIR', 'logs', PathLocation.DATA,PathType.FOLDER),
^ (bad-whitespace)

--------------------------------------------------------------------
Your code has been rated at 10.00/10 (previous run: 10.00/10, -0.00)

ERROR: Job failed: exit status 1