Improve 1-pane message visual

Also fixed the text alignment in the tabs on the 2-pane message view.

We don't yet to have the full-spec for this, so it's still temporary.

Now we again wrap the webview in a scroll view, so we'll have the "message
keeps growing" issue again.  I'll file a bug for this.

It's still temporary, so I didn't remove the scroll views for the
each section (e.g. the attachment tab).  Also I had to make up some
colors/dimensions which were unspecified.  Also I didn't always define
styles when I should.  Let's clean up these things later when we
get more detailed spec.

Change-Id: Ibdb78543f5ec7300f92091d1f8b800ca5edc74b2
9 files changed