Basic infrastructure for new texteditor component
Loading a file works
Saving files works
Refactor editor into Editor class
Enable codemirror search/replace shortcuts
Update text editor for new contents API
Override Ctrl-S shortcut to save text editor contents
Use NotificationArea in the text editor
Set page title for editor
Styling to make it clearer where the editor is
Better way of saving through CodeMirror

This should support whatever keyboard shortcuts are configured for the
'save' command.
Add filename to header area
Remove unused import of jquery
Remove unused imports in editor notificationarea
/texteditor/ in URLs -> /edit/
Rename texteditor files & folders to edit
Merge pull request #6866 from takluyver/nb-texteditor

Notebook text editor