API v2

*Contains:*
 * api is versioned to keep compatibility (v1 is default)
 * unused api routes removed
 * got rid of routes that are too deep and use more than one globally unique id
 * consistently nested json output
 * useage RABL for json output definition
 * unified error handling
 * updated apipie docs

*Known issues:*
There are several routes that were added recently to v1 and are not reflected to v2 yet. We will fix them later. We can't wait with the pull request any longer as every rebase becomes more and more complicated with time.