New taxonomy field: store parent keys on documents

In CMS-15401 we have implemented storing all ancestor keys always, e.g. in  property hippotaxonomy:keyswithancestors, so separately from which categories are selected in the picker, in the existing taxonomy field based on mixin hippotaxonomy:classifiable.

In CMS-14419/CMS-15402 a new taxonomy field has been introduced, more like regular fields, that does not have this ability yet.

The idea is to add an extra configuration property e.g. "taxonomy.path.withancestors" in the doc type editor (below "taxonomy.name") to enable this have this always, in 

• content perspective (org.onehippo.taxonomy.plugin.TaxonomyFieldPlugin)
• Visual Editor (org.onehippo.cms.channelmanager.content.documenttype.field.type.TaxonomyPickerFieldType)