CORE, RPC, GUI: support for password reset via non-authz link

- Fixed indentation of UsersManagerEntry
- Send email to user with password reset link for non-authz gui.
- Support for string encryption and decryption using AES.
- Notify user that password was changed to all his emails.
- Allow to load non-authz password reset GUI (is behind CAPTCHA).
- Allow VO admin to send password reset link to member (for allowed namespaces).
- Use Base64 encode/decode for cipher text to be safe in URLs.

- Following entries must be set to perun.properties
  perun.pwreset.secretKey=[key for aes]
  perun.pwreset.initVector=[vector]