add forgot password function

- is not fully working, I had to switch to session attributes
- some maintenance of the code is done in UserDBPeer and DataManager
forgot password - problem with database

- session scope attributes for email and activationString added
- trying to figure out, why it throws SQL Exception (in the workbench it
says no db selected and I have to add "dictatetrainer." before table
name "users" to make it work)