View files and directories

* Ability to look into files and folders for a certain commit
* Added button in commit menu
* File and folder views match the appearance of the diff page
* Breadcrumb to show in which folder / file you're at
* Binary files are downloaded instead of navigating to the view page
* User can navigate back to the diffs with the same button menu (However, there it an issue to solve when using this button in a subfolder - will look in to that)