Make shareabouts places editable in-browser

[goldpbear]

We'd like to give authenticated dataset owners/administrators the ability to edit and delete shareabouts places from within the browser interface.

Features

• Support basic editing: open a place detail view in editor mode, update title, body, and comments fields, and make a place invisible - Editor: Basic editing functionality #500
• Support editable attachments - Editor: Support editable attachments api#59
• Ingest existing landmarks data - Ingest landmark data api#60
• Make lines, points, polygons, and geometry styles editable directly from the map - Editor: Support editable geometry #410
• Support rich media features such as videos, html embeds, linkd, etc. - Editor: Accommodate landmark data in shareabouts place models #407
• Support admin-only places - Editor: Admin-only places #498
• Support admin-ony form fields - Editor: Admin-only form fields #499
• Make it possible to add unused field types to a place model in editing mode - Editor: Edit unused fields #497
• Editor "draft mode" - Editor: Draft mode #501
• Support form-only fields - Editor: Form-only fields #523
• Support image uploads in the rich text editor - Editor: support image uploads via the rich text editor #525
• Preserve landmark url style - Editor: Preserve landmark url style #549