★ New implementation of the skills system

The approach is, basically:

* Skills are objects used to track a character's skill (ie. the lines on the character sheet).
* Templates are modules that extend each relevant instance of a Skill (eg. Skill.new.extend(a_template_module)). They represent
  the skill as defined in the system (ie. the rulebook description and rules, not the specific instance for a given character).
* These modules are defined through a DSL to simplify their setup.

This approach brings true lazy instantiation to the skills system (in the previous implementation, the a character's skills objects where instantiated as soon as its profession was set, so that the level bonuses and development costs could also be set). It also handles skill categories.

This new implementation also changed the skills DSL somewhat.