[backend] improve last commit

turn around hash, a target can only exist once
[webui] do not show user pages for "deleted" users
[webui] privacy fixes, hide user data

* email adresses only visible to logged in users
* deleted users are not shown anymore
[backend] provide register target in SLE 12 also as package provides (bnc#881320)
[webui] fix submit request dialog

showing target package name by default again. The dialog failed
if package name from source and target package name is different
when constructing the request otherwise.
[webui] fix forwarding of requests

request webui api call is obsolete now
[api] revert to rubygem-mysql2 0.3.15

solves hopefully some issues with mysql/sphinx on sle 11