This commit extends the optional currently existing low level font
baking API with another more high level font atlas API.
The font atlas takes away some fine grained memory control from the
user but is easier to use and to understand than the lower level API.
I added combined with the font atlas a optional default font which
allows running the library without a user provided truetype font.
While user friendly it is quite big (~12kb) so I added a compiler flag
to remove it from the library while compiling if not wanted.
Finally I added some additional compiler flags to allow easier to use
APIs. The downside is that all of them require the standard library,
so if you don't want to add the standard C library I would recommend
deactivating all flags marked as standard library flags.
Previous visual changes in the library were quite limited with some
colors and some global properties. This commit changes all that and
provides way more control over every widgets visual appearance.
Changes include extended color selection, per widget properties and
the possibility to use skinning.
While the new API allows for a lot more control it is currently quite
low level and needs a lot more testing and probably another higher
level style API to make changes in code easier. I also had to remove
the style modification code inside the demo and will probably first
try to write another higher level API before adding it back in.
This commit also include some breaking changes to existing code like
the missing style stack API and some widget names changes due to
added granularity granted by the rewritten style.
