As a user, I can easily filter the list of visible Tests in a Test Plan's Board folder using custom fields based filters

As a user, I can easily filter the list of visible Tests in a Test Repository folder using custom fields based filters in the "Simple" tab view of the Filter dialog.

Currently, the fields available under the "Simple" tab are hard-coded.

ACs:

• the current available fields can be selected as basis for filtering
• any custom field can be chosen to be used as a criteria for filtering
• for multivalue fields, the list of possible values must be shown so the user can select one or more of them to be used as criteria for filtering