Support for padding in MTFontIconModel
Parser is now able to parse the padding settings
Turned out padding wasn't a good idea...

Now using baselineAdjustement, to be eventually combined with scaleAdjustement to try to workaround Apple's wierd way of rendering custom fonts, or my not understending of it...
Icon factory handles the adjustements + refactor

Refactor:
- MTFontIconView has to be initialized with a model
- Removed those dirty `kWorkaround...` values

Closes #23