RPC: Deserializer now can provide its HttpServletRequest

- All RPC's deserializers now takes HttpServletRequest in constructor
- Implemented method getServletRequest() which returns request for
  which is deserializer used.
- Such request and its parameters (like URL) can be then passed to
  Perun's API methods like "parms.getServletRequest()".
- Can be used to determine "where is Perun running" on runtime
  without static configuration in perun.properties.
- Updated javadoc for all related classes.
- Fixed source formatting.