Reintroduce improved hover and bar clicking

This patch mainly reintroduces the option to click on bars and move
the pointers with it. To do this, 'ghost' pointers are introduced
to show what would happen when bars are clicked. The pointers moved
differ depending on where the user clicks on a bar. Pointers are
still not allowed to change positions, so in some cases booth pointers
move with one click. See the task description.

The patch also includes some renaming and also refactoring of the
click handling in general. Furthermore bar hover mechanics are handled
by the RevisionListView class now.

Bug: T172092, T173566
Change-Id: I32a8256f7667e03081324d54accdf03a17454faf