Bug 789056: Document api-utils/system/events and use same names than nsIObserverService
Bug 804935 - TypeError: window.tabs is undefined

It was a regression during fennec implementation of windows and tabs. A `ChromeWindow` was used instead of the expected `BrowserWindow`.
Bug 783743 - addon-page should work with "index.html?[stuff]" and "index.html#[stuff]" (and both together)

- Replaced usage of `inContentWhitelist` with `hideChromeForLocation` to have more flexibility about URLs to hide
Update hidden-frame implementation.
Make frames contexts executable.
Handle subsequent loads in frames properly.
Looks like previous code was not triggering onReady event on subsequent loads, so do we do the same.
Use `iframe` instead of `browser` since location change in the browser
does not seems to trigger `inner-window-destroyed` notifications.
Use utility function to obtain innerWindowID.
Output custom logging during automated tests.
Implement JEP-Disposable.
added system.md
Actually setup a listener for disposable instances.
Implement tests for disposables.
Add missing license header.
Make data properties overridable on the instances.
Make data properties configurable to avoid incompatible changes.
Properly clean up after tests.
- Added the selection listener only to documents loaded in Tab (is consistent with other modules like PageMod)
- Avoid to handle detached selections
branched off 1.13, master is now destined to become 1.14