vps: Use a bootstrap tooltip to hint at users to install their vps before launching

Apparently it's been an issue up for debate whether the UI should make it too clear to users what to do after first purchasing their server, and I've heard there's been a lot of tickets for asking for help about it.

Hopefully this will decrease the number of users who can't figure out what to do to get their server up and running. When the panel sees that there are no tasks in the task log - which should mean the user *just* purchased their VPS - it will add a bootstrap tooltip to the "Install" button, which indicates you should install an OS to your VPS before launching it. ( see http://i.imgur.com/zqSjFno.png )

This tooltip will only be present when the mouse is hovered over a button at the top of the screen - the square ones matching `.btn.btn-block.btn-icon`, so the whole top bar vertical with the install button.

Once they've installed an OS, it should be clear what to do and their server will probably already be up and running - and the task log will be as well, so the tooltip will vanish.

Hopefully this is subtle enough to not make the panel do completely obvious things and walk users through things they obviously don't need, but rather just a small tip to help them through installing quicker.