Topcoat toolbar

This transforms the existing "#main-toolbar" structure into a vertical sidebar and renames the old white toolbar to "#titlebar."  The titlebar above the editor is only visible when inBrowser=true.

ModalBar, which used to be inserted _inside_ the top toolbar, is now inserted as a sibling to it so that it can be used even when the top toolbar is hidden.

Note: the CSS changes are based on [Garth's topcoat branch](https://github.com/adobe/brackets/tree/garthdb/topcoat-parity).