* config_tempest.py was renamed to main.py - entrypoint for console-script
(discover-tempest-config) was changed too
* TempestConf class was decoupled from main.py and moved to tempest_conf.py
file. Imports of related tests were edited and the order of imports in each
file was changed so that other dependencies are first followed by a blank
space and then local dependencies are listed.
* tests related to TempestConf class were moved to test_tempest_conf.py file
Change-Id: Idb235b969ba3c1e320aa3efa7fe77b5c59f4ffc6