DIMP javascript fixes.

DIMP javascript fixes.

onFetchUpdate()->onCacheUpdate().
Name change better reflects action - since we need to call when doing
things like deleting messages also (which has been added by this
commit).

Make sure UIDs are interpreted as a Number
Needed to correctly generate UID ranges.  Use Number() instead of
parseInt() in some places where we know we have integer data that may be
stored in a string.