Fonts FtLibraryHandler and FontHandler refactoring

[saurtron]

Work done

• Separate FtLibraryHandler into its own file.
• Move some global font config options to fontHandler.
• Centralize font Init/Kill at fontHandler.

Remarks

• At the moment font global/static code is haphazardly split among CFontTexture, glFont, SpringApp..., with the recently introduced fontHandler I'm moving some more of that logic there.
• Also split FtLibraryHandler into a separate file, since it feels out of place inside CFontTexture.
  • Extended FtLibraryHandlerProxy api to ensure ft and fc includes don't leak out of cpp files and to have a bit better decoupling.

Next steps

• Some more candidate code to moving out is all the default fonts code at glFont.
  • Will move that in a later PR, so as to limit scope of this one.
  • Probably directly under fontHandler too, but could also create a new module for those.
• There's still more work to do re: refactoring fonts, consider this a start and everyone is welcome here to voice any remarks or ideas for the future or whatever.

[lhog]

Let's comment out FcFini(); as per #2450

[saurtron]

Let's comment out FcFini(); as per #2450

Made a separate PR for that so its easier to merge into the release branch if needed: #2494

Will rebase into this one once that's in.