Bug 1109453 - Call WeakMap constructor with "new".
Merge pull request #1743 from arai-a/bug1109453

Bug 1109453 - Call WeakMap constructor with "new". r=@gozala
Implement addon/bootstrap shared module.
Read module paths from preferences.
Add filtering capability to a jpm tests.
Fix path reading.
Do not nuke sandboxes on unload as that could kill sandboxes where bootstrap is loaded.