Bug 980410 - Implementation of toolbox panel

Note that dev/volcan.js has being reviewed by @dcamp separately form this, so feel free to ignore it.
it should be related to a rendering issue that I've experienced when I tried the devtool addon panel prototype on Linux:

iframes with "remote=true" attribute are rendered correctly in a e10s window, on the contrary they are not rendered in a non-e10s window (but the content is there, e.g. we can copy and past its content as if it was rendered correctly)

https://github.com/Gozala/addon-sdk/pull/7