58789: Rest call for editing schema (returns 415 unsupported media type atm) + improvements to delete

* added metadata schema form, with the form model fields & validation and layout
* fixed the pagination for schemas and fields
* added reducer and actions for the registry state

Conflicts:
	src/app/core/data/comcol-data.service.ts
	src/server.ts

Angular6 upgrade

Hide the wrapper component when there is no text content