Bug 814273 - [email] Replace concatenated gaia-email-opt.js with the files that make it up (as a vendor code drop)

This is just @jrburke's https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/86 with a few minor review changes on top.  This is r=asuth with the required changes made, which I made :)

@mozsquib is cool with this per IRC.