_mpercolate API support, with unit and integrationtests
added similar percolate integration tests as the ones for multi percolate and unified the error handling for both, also found out that the PercolateCount() only took an object and could therefor not be used to count percolate exisisting documents, id was being serialized in the body of the percolate requests which does not do anything
Merge pull request #856 from elasticsearch/feature/multi-percolate

Feature/multi percolate