Remotepath mapping

Again a couple of unrelated base commits (same ones as the indexer PR), sry about that, but it was way easier to do it this way then dealing with the merge hell I would inevitably run into otherwise.

The last commit is about moving the Local Category Path to some global mechanism, IRemotePathMappingService. It also involves a db migration.
The service is used to store the mappings, but also to handle the translation itself.

I have some trouble with the UI. Deleting a mapping results in an api error (probably related to the backbone model url).
Also Editing one doesn't update the main table. Any hints on that are very welcome.

Please let me know what you think.

![image](https://cloud.githubusercontent.com/assets/6383890/4241349/fc31bfe6-39f2-11e4-9c4a-fcc864491492.png)