Refactoring a bug fixing.

 * Link recognization in description. Bug links are simply matched. Not
checked to exist.
 * New upstream matching patterns.
 * 'on hold' github milestone recognized.
 * 'Multiple Bug Match' no longer complains. One PR can fix multiple
bugs. Code needs further refactoring to handle that case.
Merge pull request #41 from Gonthim/master

Refactoring a bug fixing.