Removing skins from repository
Adding Generate skin atlas maven plugin

The maven plugin check if it is needed to generate the atlas (the target
location does not contain a generated skin's atlas) and generate it.
Fixes #253
Moved Ttf2FntGenerator to ead-maven-plugin.
Added mockup sources and images.
Added mockup font generator.
Merge pull request #449 from imartinezortiz/skin-generator-maven-plugin

Skin generator maven plugin; thanks to Ivan & Christian