Replace FileSystem API with chrome.storage.local

[gorhill]

Because http://code.google.com/p/chromium/issues/detail?id=389879.

Apparently The QUOTA_BYTES "value will be ignored if the extension has the unlimitedStorage permission" (ref)

I can't tell whether Chromium 37 will break HTTPSB, uBlock, (Adblock Plus, etc). Nowhere can I find feedback about this from Chromium devs. Given that FileSystem API has been dropped as candidate technology for HTML5, I will assume the worst and try to find an alternative.

Not sure if chrome.storage.local will work, I have to write prototype code.

[gorhill]

Prototype code works, so now it's to convert uBlock/HTTPSB before 37 lands.