Replace "Create new snapshots" button with icon

These buttons were taking up a lot of horizontal space on the page, and
just adding significantly to visual clutter on projects that have a lot
of URLs.

In this commit, I'm trying out using an icon next to the other icons for
the URL to improve the UI of this page. While I don't really like the
whole `method` option in principle, it is convenient here.

Change-Id: Iaf9c123f7d8c76f8382e14c299551c9c4fc24379
Prevent underline on hover for URL icons

When hovering over the icons for each URL on the project page, there was
a bit of a tiny underline following the icon that looked a little out of
place. This was happening because there was whitespace inside the link,
after the icon element. To fix this, I added some HAML whitespace eaters
around these spans.

Change-Id: Iaa3d7653e22da062e2ab206cfbd3033436602613