New Rewind, Stop, Play/Pause buttons for EdGCM

[mchandler]

The following changes/additions should be made to the run buttons:

Rewind button: Should put up a dialog that asks for a date to rewind to. We will have to implement a new ISTART capability to handle this. A short cut in the dialog box could "Restart from Beginning"

Stop button: a new "Stop" button, using the traditional square icon, will stop the simulation and quite Lunar

Play/Pause button: The Play/Pause button will now toggle between those two modes and will change based on the selected run's status. Play has the same function, but clicking on Pause will stop the run, but will not quit Lunar.

Extend (Fast Forward) button: keeps same functionality as before