Fix for Firefox 34

Passing sandboxes between translators became difficult. This change
loads all translators in the same sandbox, using the same ugly hack as
in the connectors to get us close enough to being able to load
translators into separate scopes for things to work.

Conflicts:
	chrome/content/zotero/xpcom/translation/translate.js
Update maxVersion
Maybe fix for Firefox 31

Still need to test more comprehensively
Fix MutationObserver tracking and clearing upon pageModified
Pre-patch, we were losing references to previously-registered mutation observers when the translate instance was dropped along with the Page object on every pageModified event. This was causing multiple mutation observers to get registered on the same nodes triggering more and more detectWeb calls each time.
We are now careful to disconnect all mutation observers before redoing detection for the whole tab (i.e. all documents in page)
Re https://github.com/proquest/translators/pull/1