DS-2348 REST Bitstreams should be only in original bundle.

Better logic at adding bitstream to bundle. It checks if bundle original
exists.
Removed copy-paste error
Replace finding original bundle.

Replace finding original bundle by getBundles("ORIGINAL").
Added missing bracket.
Bundles length check repair.
Merge pull request #777 from ctu-developers/REST-improvement

DS-2348 REST Bitstreams should be only in original bundle.