Pinned documents (#608)

* Migrations and API for pinned documents

* Documentation

* Add pin icon

* Fin.

* v0.2.0

* Remove pin from DocumentPreview, add general menu
Add Pinned documents header

* Tidy

* Fixed: Drafts appearing on collection home

server/api/__snapshots__/documents.test.js.snap

@@ -17,6 +17,15 @@ Object {
 }
 `;
 
+exports[`#documents.pin should require authentication 1`] = `
+Object {
+  "error": "authentication_required",
+  "message": "Authentication required",
+  "ok": false,
+  "status": 401,
+}
+`;
+
 exports[`#documents.search should require authentication 1`] = `
 Object {
   "error": "authentication_required",
@@ -44,6 +53,15 @@ Object {
 }
 `;
 
+exports[`#documents.unpin should require authentication 1`] = `
+Object {
+  "error": "authentication_required",
+  "message": "Authentication required",
+  "ok": false,
+  "status": 401,
+}
+`;
+
 exports[`#documents.unstar should require authentication 1`] = `
 Object {
   "error": "authentication_required",