Popovers

Changes:
* Added a popover menu (see screenshot), it allows you to load a magnet quicker, you just click to open it, then you can type out the whole link if you're a faggot, or you already have it in your clipboard, in that case, you can add a manget just by double-clicking the icon.
* Fixed a gui bug where deleting a torrent would make the torrent above it change name for up to a second.

I didn't know adwaita dark looked this good, big margins aside.
![screenshot from 2014-08-13 01 07 15](https://cloud.githubusercontent.com/assets/8192824/3899072/763008f6-2275-11e4-9ef2-85a48c778502.png)