Don't clear buying list on category switch + AdvTrade fixes

The buying list now acts like a shopping cart. It is no longer cleared
when switching between categories or containers. Closing the dialog or
switching to sell mode still clears it.

Also fixed:
- Filter button in sell mode
- Bug where filtering sellable list readded items already moved to
selling list
- Visual price display not clearing when remove all button is used on
buying list
- Gear container picture showing rank instead of portrait in buy mode
- Dialog is no longer closed when trying to sell zero items
- LbCurSel is now reset when the buyable list is cleared
- Category is no longer opened onLbSelChanged. Instead you need to
double click or use the "View" button, so the arrow keys can be used for
selecting too.

SQF/dayz_code/actions/AdvancedTrading/functions/defines.hpp

@@ -0,0 +1,30 @@
+#define Z_AT_DIALOGWINDOW 711197
+#define Z_AT_SELLABLELIST 7401
+#define Z_AT_SELLINGLIST 7402
+#define Z_AT_BUYABLELIST 7421
+#define Z_AT_BUYINGLIST 7422
+#define Z_AT_CONTAINERINDICATOR 7408
+#define Z_AT_ITEMINFO 7445
+#define Z_AT_SLOTSDISPLAY 7404
+#define Z_AT_TRADERLINE1 7412
+#define Z_AT_TRADERLINE2 7413
+#define Z_AT_PRICEDISPLAY 7410
+#define Z_AT_SELLBUYTOGGLE 7416
+#define Z_AT_RIGHTLISTTITLE 7409
+#define Z_AT_REMOVESELLITEMBUTTON 7432
+#define Z_AT_REMOVEALLSELLITEMBUTTON 7433
+#define Z_AT_REMOVEBUYITEMBUTTON 7442
+#define Z_AT_REMOVEALLBUYITEMBUTTON 7443
+#define Z_AT_BUYINGAMOUNT 7441
+#define Z_AT_BUYBUTTON 7436
+#define Z_AT_SELLBUTTON 7435
+#define Z_AT_ADDBUYITEMBUTTON 7440
+#define Z_AT_ADDSELLITEMBUTTON 7430
+#define Z_AT_ADDALLSELLITEMBUTTON 7431
+#define Z_AT_TOGGLECURRENCYBUTTON 7450
+#define Z_AT_CONTAINERINFO 7446
+#define Z_AT_PRICEINFO 7451
+#define Z_AT_FILTERBOX 7444
+#define Z_AT_FILTERBUTTON 7498
+#define Z_AT_DETAILSTEXT 7488
+#define Z_AT_BACKBUTTON 7449