#246 made the table in the InfoPanel sortable
 #246 switch the table back to JTabel, instead of JXTable
 #246 change the order of the images shown in the cell of JGrid
 #246 show the Aufnahmedatum in the InfoPanel
#246 align the bildnummern in the middle of their column in the table in the infoPane
 #246 added a third view in Sb_stadtbildserieAggregationRenderer
 #246 added the view to see the chosen images
 #246 fixed small bug, used the row view index instead of the model index
 #246 created Sb_AbstractPictureGridObject

This abstract GridObject can be used as a basis for other GridObject
holding Stadtbilder. Its main functionality is to download a picture
asynchronly.
 #246 the infopanel is not visible if the Warenkorb is selected
 #246 do not show selected images in the Warenkorb  which are in the bin.
 #246 simplified Sb_SelectedStadtbilderJGrid.stadtbildUnchosen()
 #246 small GUI changes