873967: Move choose server tooltips closer to the elements they assist with.

Tooltip for the subscription management service text is now closer to the text
itself. Similarly the activation key checkbox tooltip is now *much* closer,
which hopefully is more clear. The checkbox itself is now centered beneath the
server URI textbox.
851325: Anchor choose server "default" button beside the text box.
Merge pull request #864 from candlepin/dgoodwin/closetooltips

873967: Move choose server tooltips closer to the elements they assist w...