Separate exp bar and caught indicator from the rest of the gen 2 features

[senolfeldmann]

I made some of the code dependent on condition GEN_2_GRAPHICS dependent on a new conditional EXP_BAR_AND_CAUGHT_INDICATOR. The motivation behind is that I wanted to have the exp bar and the caught indicator functionality while keeping the game as vanilla as possible when it comes to the graphics (while being coloured of course). It may be that I got something wrong, so I am eagerly waiting for your feedback.

I tested only setting EXP_BAR_AND_CAUGHT_INDICATOR to 1 and the game runs fine. I did not encounter any incompatibilities with the rest of the gen 1 graphics so far. I did not test only setting GEN_2_GRAPHICS to 1 yet.