* Added checks for protected branches in pull requests

Signed-off-by: Christian Wulff <NChris@posteo.net>

* Moved check for protected branch into new function CheckUserAllowedToMerge

Signed-off-by: Christian Wulff <NChris@posteo.net>

* Removed merge conflict lines from last commit

Signed-off-by: Christian Wulff <NChris@posteo.net>

* Explicit check for error type in ViewIssue

Signed-off-by: Christian Wulff <NChris@posteo.net>

* Pull request options migration and UI in settings

* Add ignore whitespace functionality

* Fix settings if pull requests are disabled

* Fix migration transaction

* Merge with Rebase functionality

* UI changes and related functionality for pull request merging button

* Implement squash functionality

* Fix rebase merging

* Fix pull request merge tests

* Add squash and rebase tests

* Fix API method to reuse default message functions

* Some refactoring and small fixes

* Remove more hardcoded values from tests

* Remove unneeded check from API method

* Fix variable name and comment typo

* Fix reset commit count after PR merge