Added virtualenv management

Added virtualenv manager at ninja startup.
This will create a virtualenv if not present, there we will handle
all of our own packages.
Also I created a wrapper around pip functionality to allow us to
properly uninstall and install plugins, which now should be eggs
Temporary documentation on how to do a plugin has been also added
to the env manager file
Corrected translationbug and deleted wizard

Corrected translation missing string and also deleted te wizard to
re-write it.
Merge pull request #1654 from perrito666/master

WIP: Added Nenvironement