Merge pull request #100 from tanriol/fix-richtree-selection

richtree broken: nsIScrollBoxObject interface has been removed in Fx36
Disable locales not supported in dev

en-US is the only locale that is regularly updated during development, all others are updated just before release. Disable them so that Brief can be run from git even on non-en-US locales.
bump version to 2.0b2
Delay feedlist invalidation until property changes are saved

This fixes part 3 of #111 (edits to 'Include in Today view' do
not refresh the unread counts immediately). The invalidation
used to occur before omitInUnread is saved to brief.sqlite
Copy Query.folders by value

Query.folders need to be copied by value so that the list
is not modified when children are added to _effectiveFolders

This fixes part 1 of #111 (headlines mode switch not working
with nested folders)