T27791 - Optimized RT mime types

Summary:
+ Optimized check order of Dose mime type to minimize the usage of readers for pre checks
+ optimized the tag scanning
+ removed dependencies/code not needed any more after optimization
+ fixed T27791

Test Plan: review and unit tests

Reviewers: thomass

Reviewed By: thomass

Maniphest Tasks: T27791

Differential Revision: https://phabricator.mitk.org/D420