Move some non-skin-specific styles back into ve.ce.Node.css

Rules like "right-aligned images get float: right;" should
be in the generic image CSS, they're not skin-specific.

I haven't exactly teased apart what is and it's skin-specific,
this is just a first stab.

Change-Id: Ie374685d2c66e2275f7a98a590e563bf36da7f87