[Core] add ability to run generic distributed tasks on documents

[dsukhoroslov]

add methods to DocumentManagement interface:

	<T> T executeOnDocument(String uri, Callable<T> f, Properties props) throws BagriException;
	<T> ResultCursor<T> executeOnDocuments(Collection<String> uris, Callable<T> f, Properties props) throws BagriException;

also can add two more methods to run EntryProcessors. But it must be some standard interface, unrelated to HZ lib.

Implementation of the tasks passed by client to the methods must be supplied by client via registered in Bagri libraries.