Require strict mode everywhere and enforce it with JSHint

Don't fail silently, and enforce immutability everywhere.

This change also uncovered some bugs.

* A regexp in WikiConfig was not actually matching $1, and in turn tried
  to modify the frozen baseconfig

* parserTests tried to modify the base config too

* core-upgrade used some dodgy ternary operator with global, which was 
  flagged by jshint

Change-Id: Ia618baecd850fbb215fa80403b67e2d9bc53597b