* UI: Move ApplicationContextMenu in a separated class
This PR remove duplicated code related to the context menu on the Application list/grid by create a control for the menu which include related handler.
I've renamed "GameList/GameGrid" by "Application" for consistencies. And I've removed all uneeded field from the project file too.
While I cleaned up things, I've found an issue about purging Ptc/Shader cache, both methods list files even if the user say "No", shader cache is purged even if the user say "No". It's fixed.
* Adresses feedbacks
