GUI: skip captcha for specific VOs

- 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.
GUI: fixed mail notifications tab opening for different vos/groups

- Fixed hashCode() and equals() to check also groupId parameter.
GUI: check for similar users by commonName too on application form

- 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.
Merge pull request #426 from zlamalp/captcha

GUI: multiple fixes to application form and notifications