Fixes for array update documents and checkbox fields, plus a couple small tweaks

Hi Eric,

I found a couple issues during the transition to Blaze (d1f071f & bd627fe).  I also needed to tweak semantics slightly for my workflow (cb2bd5c & eb25c72).  Let me know if you have any issues with those changes and I can break out the bug fixes into a separate branch.

Cheers,
 Greg