add a .gitignore file, same thing as .bzrignore
fix error when %recipients is empty

https://bugzilla.mozilla.org/show_bug.cgi?id=904467
add order to extension paths.

it's better to be explicit than to rely on glob() magic.
some extensions have side effects: order matters.
some extensions need to be first / last.

this adds a @extension_paths setting in localconfig.
(similar to django's settings.INSTALLED_APPS)

https://bugzilla.mozilla.org/show_bug.cgi?id=908087
add extension as a submodule
this will need commit b6c58fc7be71d36e788803e027f8c60f91c744b8 as a pre-req.

https://github.com/dnozay/Bugzilla-Extension-MultipleEditNoEmail
https://bugzilla.mozilla.org/show_bug.cgi?id=23924