Enhancement request: add support for importing fnt files exported from Angelcode's Bitmap Font Generator

[cogburnd02]

Bitmap Font Generator can be found here:
https://www.angelcode.com/products/bmfont/

and this also adds compatibility with LibGDX' Heiro tool, here:
https://libgdx.com/wiki/tools/hiero

Finally, a description of the file format in question can be seen here:
https://www.angelcode.com/products/bmfont/doc/file_format.html