Firefox 4 no longer unpacks XPI files by default

[James Henstridge]

When installing from an XPI, Firefox 4 no longer unpacks extensions by default. This is a problem since we want to execute a script stored in the extension's directory. Apparently we can force Firefox to unpack the extension with the <em:unpack> element in the install.rdf file:

https://developer.mozilla.org/en/Install_Manifests#unpack

This probably isn't an issue if Bindwood is installed from an Ubuntu package, so isn't necessarily a blocker for the next release.