Aes encrypted config cleanup

* unit tests 
* tested on webcube 4.3
* added serialize and deserialize methods to ConfigurationInstance
* fixed site selection on form

Three questions:
1) Does IV need to be 16 bits?: http://codeghar.wordpress.com/2011/09/01/aes-encryption-with-python/
2) If the IV acts as salt then perhaps we should add a salt field.
3) Are sites allowed to share secret keys and should they be allowed to access other site's configurations?