Another fix for an possible null value
Various cleanup/changes -

* Some fixes for thunderbird integration
* Better Conkeror support (still broken)
* Cleaned up some bad variable assignments
* Added notes and localization stubs to install.rdf
Changed update_translations.sh to be less project specific
Removed persistence flag as it causes issues with being inactive
Changes for v0.9.3

* Updates to Options/About pages
* Moved global var jq to webpg.jq
* Added Secure Editor; closes #37
* Improved GMAIL support for new compose/reply
* Moved to MutationObserver in place of DOMSubtreeModified when available
* Replaced textarea menu with toolbar
* Fixes to dialog placement
* Fixed z-index order of toolbar menu
* Replaced dialog button text with translatable strings