explicitly use components for some dependencies

Some projects have special repos for bower [components][]. jquery used to come from here, but something changed, and now it points to jquery/jquery, which has a bunch of extra stuff we don't want.

[components]: https://github.com/components

This changes our `bower.json` to use the components source explicitly for:

jquery, backbone, font-awesome, underscore

some things are available from components, but are not used:

- bootstrap, because it lacks the .less parts, which we use
- highlight.js, because it lacks unminified source, which debian doesn't like

I also updated the .gitignore to exclude a few more common files that are irrelevant.

I left the copyright changes that affect bootstrap uncommitted, because we will update bootstrap to 3.0 soon enough.