Add callback methods to omero.scripts.client

[jamoore]

After discussions (Apr 12), scripts should have a mechanism for requesting more information from the user and informing the user about the current status of the script ("0.5% finished", etc.)

This will require work on the notification system (#2169)

Proposal:

 mainJobParams = omero.grid.JobParams()
 mainJobParams.name = "imageProjection" # Name of script
 mainJobParams.inputs = {"image" : omero.grid.Param(...)}

 secondaryJobParams = omero.grid.JobParams()
 secondaryJobParams.name = "z" # Name of step
 secondaryJobParams.input = {"z" : omero.grid.Param(...)}

 # Define a script which takes an image
 c = omero.scripts.client("name",\
        mainJobParams,
        callbacks = [
            secondaryJobParams
        ])

 values = c.callback(index=0, timeout = 5)
 # or
 values = c.callback(name="z", timeout = 5)

 c.progress(percent = 0.5, step = "Downloading", index = 5, total = 100)
 c.exception(exception = ex)

 # Possible future additions:
 c.checkpoint() # saves all the session items

Suggestions welcome