Add new feature flags - mobileid, precompile_asmjs, hardware_512mb_ram (bug 1097428)

https://bugzilla.mozilla.org/show_bug.cgi?id=1097428

Code to use buchets in reviewer tools is removed because it doesn't work properly anyway, as feature detection of privileged APIs doesn't work in the browser.
Nothing, I'm removing it completely from zamboni - it was only used by reviewer tools, and I'm removing buchets filtering in reviewer tools because the in-browser detection is not reliable.