Major revision of comment system.

- Comments are stored in HTML as well as Markdown, so that conversion
  only happens when saving (rather than when viewing).
- Added 'markdown' Jinja filter for easy development. This is quite
  a heavy filter, so it shouldn't be used (much) in production.
- Added CLI command to update schemas on existing node types.

src/styles/_utils.sass

@@ -577,3 +577,19 @@
 	display: block
 	max-width: 100%
 	height: auto
+
+
+.flash-on
+	background-color: lighten($color-success, 50%) !important
+	border-color: lighten($color-success, 40%) !important
+	color: $color-success !important
+	text-shadow: 1px 1px 0 white
+	transition: all .1s ease-in
+	img
+		transition: all .1s ease-in
+		opacity: .8
+
+.flash-off
+	transition: all 1s ease-out
+	img
+		transition: all 1s ease-out