* added new events for the new reaction fire proposal that are triggered whenever a target is added or removed
* hide data layout of some ReactionFireTarget loops
* reduced cyclic complexity
* fixed some SDL2 related mouse input problems (wheel not working)
* use UTF8_CONTINUATION_BYTE macro
* get the next utf-8 character from a given string
* first step to use the text input api from sdl2
* whitespaces
* use the on-screen keyboard for sdl2 for android and ios in text input mode