Replace JsonCpp with dynamic_t. Part 1.
Adapt to the Core changes.
Adapt elasticsearch plugin to the Core changes.
Renaming protocol specification file.
Drop unnecessary source definitions in CMakeLists.txt
Code style.
Workaround deferred move-only semantics.
Elasticsearch: refactoring.

 * elasticsearch endpoint string is now const.
 * tiny renaming done.
 * more concrete template argument names.
Elasticsearch: let the compiler deduce template arguments itself.