Issue #166 Improve RESTful urls for web backend

Change create and delete urls for feeds and folders:

    POST /feed - Creates a feed
    DELETE /feed/:feedId - Deletes a feed
    POST /folder - Creates a folder
    DELETE /folder/:folderId - Deletes a feed
Merge pull request #206 from xemle/restful-urls-for-backend

Issue #166 Improve RESTful urls for web backend