Simple elasticsearch plugin added.

* at this moment it can only do get by index request and data indexing.
ZeroMQ plugin: constantness fix
Elasticsearch Service: redesign.

* index, get, search methods are supported
* delete index support will be available later (as swarm can make DELETE requests)
CMakeLists.txt updated.
Elasticsearch Service: debianization.
Merge branch 'master' of github.com:cocaine/cocaine-plugins
Elasticsearch Service: license headers added.
Changelog bump.