Further fixes to the Users module, added hybrid login (#488)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | --
| Fixed tickets | #488
| Referenced tickets | #900, https://github.com/zikula-modules/Legal/commit/5741932e22e218bf274bc81feffe1223c62380f1
| License       | MIT
| Doc PR        | ---

This PR fixes uncountable bugs :-) and adds hybrid login as @phaidon suggested in #488.