UserList improvements
Userlist improv.: Fix indent. Use iterator again.

* Plus a string fix.
Filtered Userlist: Refactoring. C

* Move logic into methods (in UserEdit)
* Minor formatting
* Fix memory leak (delete ueli if not passed to QTreeWidget
* Show filters and stuff when lastchantreestring is not empty, as that should always have something
(It even has something when no data comes from server though.)
fix indent
Improved Userlist: Refacs.

* Use boost::optional for explicit no data
* Move logic into method
mapping logic into protoUserToUserInfo
Userlist Improvements: Use RPC callbacks as well.

* Make getRegisteredUsersEx use RPC callbacks
* Implement UserInfo constructors
Userlist improvement: Use plural form translation
Userlist Improvements: Display localized time. Refactoring.

* The last seen datetime is now displayed in the local(ized) timezone.
* Code refactoring.
Userlist improvements: Use QDateTime.

* Use QDateTime wherever possible.
* Code refactoring
Merge branch 'pr-userlist'

Integrate feature branch for filtered and improved registration list.
This merges pull request #148.