CORE: fixed indentation of UsersManagerEntry
CORE, RPC: support for non-authz password reset

- Send email to user with password reset link for non-authz gui.
- Support for string encryption and decryption using AES.
- User itself or vo admin can send the email.
- Notify user that password was changed to all his emails.

- Following entries must be set to perun.properties
  perun.pwreset.secretKey=[key for aes]
  perun.pwreset.initVector=[vector]
CORE, GUI: support for non-authz password reset

- 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.
CORE: reworked password reset security

- Every pwd reset request is stored and can be used only once.
- Delete all pwd reset requests when deleting user.
- Pwd reset request is valid only for limited time since creation.
  (Default is 6 hours, actual value is taken from perun.properties).
- Use encrypted values of user_id and unique request_id to prevent malicious
  pwd reset by somebody else.

Required properties in perun.properties are now:

perun.pwdreset.secretKey
perun.pwdreset.initVector
perun.pwdreset.validationWindow
Merge pull request #324 from zlamalp/reset

CORE, RPC, GUI: allow non-authz one time password reset