create random db pw if needed

* read mysql pw from mediatum_db_pass file if pass var is not set
* generate pw if mediatum_db_pass does not exist
* secret_passwords.yml not used anymore
use supervisord to manage mediaTUM process

* supervisord starts mediaTUM and automatically restarts on failure
* removed debian initscript and upstart config file
added pause at the end (commented out)

* chance to manually kill processes which are listening on the mediaTUM port