GUI: Removed cross-site scripting hack for devel

- Cross-site scripting is no longer possible for development purpose.
  Use local Apache server and Tomcat or Jetty to run Perun locally.

- New JsonClient is not limited to standard timeout of 30s and
  waits for Apache timeout/response.

- Json(Post)Client now handles 401 and 500 responses as onError().
  For 500 also determine, if it was timeout (longer than 5 minutes).

- Removed unused stuff and properties, source format.
GUI: handle also 503 error for JsonClient
GUI: handle 404 case in JsonClient

- Tomcat returns 404 HTTP status code while redeploying webapp.
- We expect, that JsonClient always call valid URL (RPC), so
  exception text inform about server being restarted.
Merge pull request #546 from zlamalp/json

GUI: removed cross-site scripting hack