working on bulk setting when assigned/due dates for problems

Doesn't quite work because the GWT date picker widget
doesn't behave correctly when used in a dialog.
Probably need to find a way to allow the UI to appear
inline.
support running the webapp in GWT super dev mode
float datebox and timebox popups to above dialogs

We set gwt dialog boxes to a high z-index to ensure
they are visible above Ace editor instance.
Any popups (such as date/time choosers) shown in a
dialog must have an even higher z-index.
implemented bulk setting of when assigned/due dates/times

One issue remains: the local timezone isn't taken into
account.  Should be a simple adjustment relative to the
UTC time produced by the date/time pickers in the UI.
bulk setting of assigned/due dates/times seems to be working

Did conversion to local time (from UTC), and also reload the
problems (since the assigned/due dates/times have changed.)
minor refactoring (don't put an RPC method in a Runnable)
when setting assigned/due dates/times, use local time consistently