Bug 1012981 - Generate unique password and show it to the user

Replaces the static password to more secure unique, generated password and shows it to the user:
* when creates the application from the web ui
* when creates the app with `rhc app create --from-app [...]`
* when creates the cartridges and pushes the quickstart via git

[Bug 1012981](https://bugzilla.redhat.com/show_bug.cgi?id=1012981) (and also [related](https://bugzilla.redhat.com/show_bug.cgi?id=1013684))

[Trello card](https://trello.com/c/RsENlXNV/257-5-fix-5-existing-bugs)