Implement mechanism to extend MFTF Actions from outside the framework package

[okolesnyk]

Value/COD
To unblock teams from MFTF releases they can create an extension to MFTF which will provide a new Action to list of default MFTF actions.
Will also eliminate need to keep in MFTF very narrow and single project oriented actions.
Example: "waitForPwa"
Open Questions:

• How to deal with conflict actions?
  AC

[jilu1]

This is completed in MFTF-3.0.0-RC1.