If the uBlock extension is installed globally for all users on a machine, a user's first run of Firefox will fail to load uBlock because the call to appShell.hiddenDOMWindow will throw an exception. A second run of Firefox will load uBlock successfully.
The change will skip the call to onReady if the reason for the call to startup is because the addon is being installed.
Initializing the extension with AddonManager takes too long (at least for
this extension).
When starting the browser, tabs loaded before the extension could, and
because of that, blocking didn't work.
It works better, if it's initialized when the window's DOM is ready.
Pass the extension data (name and version) as the fragment of the URL
for the background script, so vAPI.app can be filled without using XHR
to read the manifest files.
