Add SCRAM-SHA1 support

Factor out GS2 tokanization into own class
Add authentication exception class

Fixes #71
Spelling fix in German translation
Spelling fixes in Italian translation
Make licenses info untranslatable
Merge pull request #667 from SamWhited/licensesuntranslatable

Make licenses info untranslatable
Merge pull request #666 from SamWhited/localefixes

Spelling fixes
Improve auth error handling and state machine
Merge pull request #665 from SamWhited/issue71

Add SCRAM-SHA1 support