refactor the player.h/player.cpp files

We often end up modifying the server/libFunq/player\* files (that's normal this is our tested application entry point!). It is now pretty big, and a bit hard to read.

I think a good first step would be to move the context locators (ObjectLocatorContext, WidgetContextLocators, etc) in a new pair of .h/.cpp files:object_locator.h and object_locator.cpp for example.
