added event actions (active screen elements) for global animations

added event actions (active screen elements) for global animations

This change adds more event actions to the "anim_event_action" option
for clickable global animations, this time adding active screen elements
(currently limited to a selection of screen elements in the main menu).

For example, you can now use:

global.anim_1.part_1.MAIN.anim_event:            click
global.anim_1.part_1.MAIN.anim_event_action:     menu.button_game

When clicking this global animation (on the main menu screen), the
game will be started (by triggering the "start game" menu button).

To dump a list of all available event actions for global animations,
blindly type the "cheat mode" style shortcut ":dump-event-actions" or
":dea" in the main menu.