Added functionality for generating complex protein descriptions.

describe.py:
- Added functionality to detect frame shifts.
- Modified the RawVar class to support protein descriptions.
- Added the core protein description function.

models.py:
- Modified the RawVar class to support protein descriptions.


git-svn-id: https://humgenprojects.lumc.nl/svn/mutalyzer/trunk@595 eb6bd6ab-9ccd-42b9-aceb-e2899b4a52f1