[Broker-J] Query REST API improvements

Existing broker REST API (including broker query API) doesn’t support such functions as aggregation, grouping and using nested logical operators, which could be useful for gathering broker statistics and reporting.

We suggest to add a new POST method for the endpoint /api/latest/querybroker and supply search criteria using JSON body. (Existing GET method implementation should stay without changes for keeping backwards compatibility and because of difficulties of parsing complicated search conditions from URI parameters when using GET request method).

The new functionality should add

• logical OR operator (absent in current API)
• aggregation operators AVG, CNT, MAX, MIN, SUM
• grouping aggregation
• new numeric / datetime / string functions