GUI: multiple fixes to application form and notifications

- Added property "vosToSkipCaptchaFor" to /etc/perun/perun-web-gui.properties
  which can contain list of VO's short names.
- GUI will skip catpcha request for such VOs and theirs group applications.
- Fixed hashCode() and equals() to check also groupId parameter on Notifications tab.
- When checking for similar users, if displayName is empty, try to use
  common name to.
- For check when application is submitted also check displayName attribute,
  not just lastName.