Make put of nil maps (and a few other cases) work pre-VOM2
Make put of nil maps (and a few other cases) work pre-VOM2

This involves more tests of the field package, a rewrite of deep equals, a small hack to make slice settable (which will go away for VOM2) and a few other changes.

Change-Id: Ie2048a934570caa0b823c3d0cb149b0c5fc13fdd

vanadium/js,vanadium/js,vanadium/js,vanadium/js