Remove util.common.makedirs

Not used anymore.
Use pkg_resources to load base config

This means less dependencies on the file system.
Move 'plugin' and 'config' modules to 'madgui.core'
Move widgets to 'madgui.widget'
Remove useless 'print' statement
Move docopt usage string to 'core.app'

(where it belongs..)
Use 'madgui.__version__' in setup.py
Remove unused OnPaint handler
Merge branch 'structure'