Adds license to project files. Before using this command, you should:

1. Edit the file AUTHORS to include your authorship (this step is automatically done
if you directly launch 'quickly release' or 'quickly share' before changing license)
In this case, license is GPL-3 by default.

2. If you want to put your own quickly unsupported Licence, add a COPYING file containing
your own licence and execute $ quickly license other.

3. Executes either 'quickly license' or 'quickly license <License>'
where <License> can be either:
- GPL-3 (default)
- GPL-2
- other

This will modify the COPYING file with the chosen licence (with GPL-3 by default).

Updating previous chosen Licence if needed.

If you previously removed the tags to add your own licence, it will leave it pristine.

If no name is attributed to the Copyright, it will try to retrieve it from Launchpad

(in 'quickly release' or 'quickly share' command only)

Finally, this will copy the Copyright at the head of every files.

Note that if you don't run 'quickly licence' before calling 'quickly release' or 'quickly share',

this one will execute it for you and guess the copyright holder from your

launchpad account if you didn't update it.