As a follow up to SOLR-5287, this is the UI related part for implementing a file-viewer and the possibility to change files (like schema & config) via the UI.
Allow at least solrconfig.xml and schema.xml to be edited via the admin screen
Admin UI - Allow creating new Files
Admin UI - Reload Core/Collection from 'Files' Page
Admin UI - Remove separated Pages for Config & Schema
Add managed schema to the list of files the admin UI cannot edit