Tweak project page buttons.
Changes:
- Add icons to the "New X" options
- Change "New git branch" and "New git tag" to "New branch" and "New tag"
- Remove "New project member" option, since it's less common than the other 4 options and didn't actually link to a "New" page, so it wasn't any better than choosing "Members" in the sidebar.
- Add "Download" text to the download button
- Add "Clone" button to toggle clone panel (still in the same location below the buttons)
