[Core] Improves FileCollection: Now implements InputFilterProviderInterface

* Method setFileValidator to attach an validator to the FileInputs.
* Fixes Form: Inputs are attached twice for fieldset implementing InputFilterProviderInterface
* Fixes translation: Wrong strings in Validator translations.

(refs #4688)
[Applications] Adds mimetype validator to attachment file inputs.

* If configured in module.config.php key ["Applications"]["allowedMimeTypes"],
  a mimetype validator is attached to the file inputs.

(refs #4688)
Merge branch 'feature/Validate_file_uploads' into develop
Merge branch 'hotfix/0.3b.1' into develop
Merge branch 'hotfix/0.3b.2' into develop
[Applications] Fix: List filter parameters are stored in session even if requested format is json

Now, if "format=json" is given as query parameter, stored filter parameters are ignored.
[Applications]: Makes item count per page for applications list configurable via query parameter
[General] Fix: Trailing comma in composer.json

(refs #4715)
[Application] Settings von Auth hierher verlegt
(#4710) Job-Import DateTime-Strategie hinzugefügt
[settings] mail
Merge branch 'feature/Settings_DynamicNavigation' into develop
(#4706) Label im Setting Mail-Container
[Core] Adds new MailService.

Mails are now handled as Plugins like Controller Plugin or View Helpers.
This allows for a maximum of flexibility.
[Settings] Storing of Mail texts handled by Settings module.
[Applications] Improves the mail handling drastically
Merge branch 'feature/Improve_Mail_Handling' into develop
[Core] Removes file validator from FileCollection
Merge branch 'release/0.4'