Many fixes and improvements

Here is big set of fixes and improvements. I tried to implement a feature or a fix in separate commit so it would be easier to look at what have been done.

Main feature/fix is user password - it includes fix for #19 and feature to edit/reset user password on user edit form.

There is one thing that breaks backward compatibility - I had to change ZfcUserAdmin\Service\User::create and ZfcUserAdmin\Service\User::edit to extract form validation into controller and add validation to edit action.

Also I removed hardcoded mail function from create action - this can be easily be added to some custom module using event manager.