Leginon

Make a more clear concept of "Target" in GUI. There is a Target class defined in TargetPanelTools.py, but it is not used exclusively. Sometimes targets are only represented as a list of x,y tuples. We need to have a direct reference from a GUI Target to a AcquisitionTargetData object when it exists. Also need to review how MosaicClickTargetFinder handles "submit" and "refresh" to avoid common problems with submitting same targets again.