Strings for PR #5653 (branch pflynn/latest-compatible-ext)
Revised strings for installed out of date extensions
Merge branch 'pflynn/strings-latest-compatible-ext' into pflynn/latest-compatible-ext

Conflicts:
	src/nls/root/strings.js
- Update Extension Manager UI to use new warning string
- Add more unit tests for Extension Manager install/update button state &
ExtensionManager.getCompatibilityInfo() utility
- Fix crash when calling getCompatibilityInfo() directly on an installInfo
(instead of registryInfo) - though I think this now only happens in unit
tests
- Ensure getCompatibilityInfo() never returns isLatestVersion unless
isCompatabile is true