Refactor: ContentInput vs ContentEditor

Currently there is quite a mess around creating and editing Content.

Come up with a proper architecture without unnecessary special-case treatment in the templates where ContentInput or ContentEditor components are used.

Mind the possibility of custom components for various Entity types or CompositeContentConfigurations.

Ideally, this should create a convenient way of using ContentInput via v-model directive aligning with vue/Quasar native components.

Document architecture when done!