Added previous order dependent filtering.
Added ability to insert or remove orders in the list.
Add Order button will change to "Insert Order" if an item in the orders list is selected.
when inserting or removing orders in the PlottedMovesListBox, the order (in the PlottedMovesListBox) stays selected.
keep action list item selected when another target entity is selected.
Fixed some crashing issues when the last item in the PlottedMovesListBox was selected and removed.
OrdersFiltering checkbox now works.
Merge pull request #24 from se5a/master

Orders filtering improvement