fixed #254 memory leak fixed by using a WeakHashMap and by removing items in a finally block
Merge branch 'bug/254-memoryleak-iconfactory' into dev
 #255 created Sb_auftraggeberToStringConverter

This String converter creates a String with the follwoing format 'name
(amt)'. If the amt is null, then only the name is used.
jalopy
Merge branch 'feature/255-ToStringConverter-for-Sb_Auftraggeber' into dev
#246 created Sb_stadtbildserieAggregationRenderer Sb_stadtbildserieGridObject and Sb_stadtbildserieGridRenderer
#246 changes to load the images from a Serie
#246 make better use of the cache
#246 use priorityqueue in threadpool
#246 keep a reference to the last shown image in Sb_stadtbildserieGridObject
#246 added jgrid to pom
#246 moved the preview image panel from Sb_stadtbildserieEditor to an own class
#246 added the  Sb_stadtbildserieAggregationRendererInfoPanel to the Sb_stadtbildserieAggregationRendererSb_stadtbildserieAggregationRenderer
#246 the table in Sb_stadtbildserieAggregationRendererInfoPanel is refilled properly
#246 table: slight improvements
#246 jalopy
#246 modified the selection of the single statdbilder
#246 simplified the ListSelectionListener in Sb_stadtbildserieAggregationRenderer
#246 being able to lock the info label
#246 create the lockableUI every time it is needed