FEATURE: support uploads for themes

This allows themes to bundle various assets

test/javascripts/admin/models/theme-test.js.es6

@@ -0,0 +1,17 @@
+import Theme from 'admin/models/theme';
+
+module("model:theme");
+
+test('can add an upload correctly', function(assert) {
+  let theme = Theme.create();
+
+  assert.equal(theme.get("uploads.length"), 0, "uploads should be an empty array");
+
+  theme.setField('common', 'bob', '', 999, 2);
+  let fields = theme.get("theme_fields");
+  assert.equal(fields.length, 1, 'expecting 1 theme field');
+  assert.equal(fields[0].upload_id, 999, 'expecting upload id to be set');
+  assert.equal(fields[0].type_id, 2, 'expecting type id to be set');
+
+  assert.equal(theme.get("uploads.length"), 1, "expecting an upload");
+});