[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request webui api call is obsolete now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
[webui] fix error handling when submiting package without change, but given target package name
[api] avoid diffing not yet existing packages

when creating submit requests with given target
[api] accept maintenance release without source changes

it may only transfer new rebuild binaries
[api] fix test cases trying to submit unchanged sources
[backend] fix syntax of register-target product provides
[api] fix search for sphinx 3.1.1
[dist] require sphinx 2.1.8 searchd
[api] revoke auto-accept requests if they can not be applied anymore
[api] Fix wrong classname for UserLdapStrategy methods

Commit 8ad64791400f60e03ab336b63ac64b1f79f6fab8
moved ldap related methods out of User class
into a new UserLdapStrategy class and Configuration class
but didn't update the caller in other places
[webui] don't link to raw log for inherited packages in staging prjs
[webui] always use the configured url for comment links
Fix/Enhance obs_mirror_project

Add back obs_mirror_project script deleted in commit a91447c5af2869ed518f8934357e173bfd723005
and fix/enhance with the following:
1. Include 'optparse' to parse commandline options
2. Verify user inputs from commandline options
3. Handle existing file by comparing file size
4. Download retry up to 3 times in case temporary network interruption