Merge pull request #1 from Tuitio/master

Add code to support new versions of Thunderbird
Rmv unpack directive from install.rdf for AMO, change homepageURL to repo
Add user-facing version notes for new version
Add AMO link and desc. to README
Reduce code in language files (also avoids warnings at AMO upload time for attempts to redefine globals)
Add type=2 to install.rdf indicating it is an extension to avoid notice at AMO; add back unpack directive until can resolve path issue; remove version for build
JSLint-inspired or required changes; JSDoc; fix issue with last style not being set