#120 created BillingBillingEditor
#120 save billing changes, when it is changed
#120 jalopy + minor changes
#120 created BillingWindowSearch
#120 created BillingBillingToStringConverter
#120 created BillingBillingRenderer and improvements in BillingBillingEditor
#120 in BillingWindowSearch only one or both kostenart can be selected
#120 use RequestsFullSizeComponent for BillingBillingEditor, BillingKundeAggregationRenderer and BillingKundeRenderer
#120 reorganized GUI elements
#120 after the creation of the Rechnungsanlage, filter the billings again.
#120 added whitespace to Storno text in BillingBillingEditor
#120 in TimeFilterPanel, the toggle buttons are now aligned with the filter panel
#31 the time filter can be ignored
#120 if the user changes a filter in the renderers, set another text in the label above the results
#120 changed text of the ignore panel
#120 added ActionListener to tbtnIgnore in TimeFilterPanel
#120 In TimeFilterPanel and VerwendungszweckPanel: check if filterAction is not null before using it. In TimeFilterPanel set the current month and quarer.
#120 changed title of BillingKundeAggregationRenderer and BillingKundengruppeRenderer
#120 in BillingKundeRenderer: open the downloadmanager when starting a download