Added fork and monitor options to dnet_run_servers

Fork option makes possible to use forking instead of running
several servers in one process.
Monitor option makes possible to disable monitor.
API polishing

Removed most of const_cast's uses. Added move semantic to async_result
Places binaries to correct packages

Added installing of dnet_run_servers to -dev package.
Merge pull request #442 from euroelessar/master

Polishing changes