- MycroftSkill and related core functions to mycroft_skill.py
- FallbackSkill to fallback_skill.py
- Add important classes decorators and functions to __init__.py
- move SkillGUI class to the enclosure along with the other enclosure
interfaces
core.py retains the same members as previously by means of imports to
retain backwards compatibility. When most of the available skills starts
using this new structure properly