Added bugfix for Ext.MessageBox. Removed old bugfixes from AskPanel &
NewQuestionPanel.
Merge branch 'master' of git@scm.thm.de:arsnova/arsnova-mobile.git
Display Markdown and Mathjax in answers

This basically works, but needs more fine tuning:

- all fields have excessive padding that needs to be reduced
- statistics are broken when Mathjax is active
- some preview buttons are missing
- long answers in QuestionDetailsPanel do not overflow