Refactor ShellScripts

Although I'm trying to keep as much functionality and responsibility as possible on drush,
there's still a lot of ShellScript code needed to make this thing work.
At the moment most of it looks pretty ugly, not easily understandable, readable, maintainable and extendable.

Proposed solutions:

• Put even more responsibility on drush
• Convert ShellScripts to drush modules
• Rewrite ShellScripts and make them Object Oriented using ooengine (https://github.com/patrickd-/ooengine)