Slight refactor.

Remove all `else` keywords from __invoke()
Add enableRegistration option

Adds enableRegistration as an option when embedding the login form on a page
Fix: Avoid FQCN
Fix: No need to alias
Fix: Keep imports sorted alphabetically
Fix: String vs string
Fix: Remove unused imports
Fix: No need to weirdly wrap implements
Fix: No need to wrap, especially not with 1 space indent
Fix: Sort extended interfaces alphabetically
Fix: UserEntityInterface should probably be UserEntity
Fix: Field is undefined
Merge pull request #495 from localheinz/bugfix/undefined-property

Fix: Field is undefined
Merge pull request #493 from localheinz/bugfix/extends-wrapping

Fix: No need to wrap, especially not with 1 space indent
Merge pull request #489 from localheinz/bugfix/fqcn

Fix: Avoid FQCN and useless aliasing
Merge pull request #492 from localheinz/bugfix/implements-wrapping

Fix: No need to weirdly wrap implements
Merge pull request #494 from localheinz/bugfix/undefined-class

Fix: Undefined class
Merge pull request #471 from chadicus/master

Add enableRegistration option to ZfcUserLoginWidget::__invoke()
Merge branch 'localheinz-bugfix/unused-imports'
Fix mergeconflict