This fixes the problem of having to "hide" the update action
in the row's actions column. Fixes bug 948397.
Additionally, added some protection for spillover between
the attrs dictionary on action instances. Fixes bug 954592.
FWIW, the code involved in the AJAX updating is largely identical,
it's just been moved from Action to Row and had few data accessors
renamed to account for the differing relation to Table and Row.
This also allowed the javascript to be significantly cleaner.
Change-Id: Ic8932a33ca6956a56c8eee09bb0a4d1f59e0ab3a
753ebd673c