Enable cookies in brackets-shell

[jasonsanjose]

Looks like cookies are disabled by default for file: URLs in CEF https://code.google.com/p/chromium/issues/detail?id=535, requires --enable-file-cookies.

At some point the PSD Lens team will transition to an OAuth workflow that will require cookies.

[peterflynn]

This might also be required for whatever metrics solution the "Brackets health report" feature winds up using

[peterflynn]

Reviewed - Closing since we have a decent workaround now: a "reverse polyfill" that reimplements basic cookies using localStorage. We can move that code into core if needed.