feature(nemesis): Extract Nemesis discovery mechanism into separate class

* Add NemesisRegistry class
  * It is Responsible for discovering and filtering NemesisClasses and disrupt methods
  * Doesnt need to instance Nemesis class
  * Reduced number of method comapred to previous:
    * get_disrupt_methods for filtering, takes in logical_phrase
    * gather_properties for exporting
* Change nemesis.yml structure
  * Now it is a pure dict, instead of list of strings
* test_nemesis_sisyphus.py no longer needs Fake classes to generate the .yml files
* Speed up nemesis discovery by checking source code only for the disrupt method

Author: pehala