gui: Move action functions to function pointer map.

This allows the functions to be more readable and make
doActions readable.

Patch set 5: gui: remove threading in GUIAction

Multiple actions were started in another thread that was joined
immediately after starting it, so the input thread was blocked anyway.

Selected single actions were started in their own thread, but this
caused bugs like being able to install the same package twice in
parallel by quickly swiping the slider twice.

Change-Id: I28adadaedd032efc7bff3aaa48e659627aa3a3b3