Upgrade to Bootstrap v2.3.1
Attach tooltips to body.

Otherwise the tooltips inherit the style of the inputs they are
attached to, especially .input-append or .input-prepend.

Both set white-space: nowrap however, which conflicts with
the pretty long tooltip texts.
Don't enforce signature in HTML frontend, closes #30
Merge branch 'wip-bootstrap-update'
Bump version number to 0.4.3
Bump MaxVersion to 23.*