Allow to build GUI with custom rpc path modifier

Like: /perun-rpc-devel/jsonp/ --> /perun-rpc-devel-zlamalp/jsonp/
Just pass -Dgui.url.modifier=[value] to maven during build.
Merge pull request #26 from zlamalp/gui

Allow to build GUI with custom rpc path modifier
Notifications: Edited notifications data access objects, so as they return an object with id defined, when save{object} methods are called from notificationsManager.
RPC: Edited NotificationManagerMethod, so as it passes the returned object in saving methods.
Merge pull request #27 from jirmauritz/notifications_Java

Notifications: Methods for saving object to DB return that object with ID set. (also changed in RPC)
Do not use ident for java files (in .gitattributes)