Shorten a UI string and update Credits some more.

Author: Cervator

main/src/org/destinationsol/game/screens/MenuScreen.java

@@ -92,8 +92,8 @@ public void updateCustom(SolApplication cmp, SolInputManager.Ptr[] ptrs, boolean
       g.setPaused(false);
       im.setScreen(cmp, g.getScreens().mainScreen);
     }
-    myDoNotSellEquippedControl.setDisplayName("Can't sell equipped items: " +
-            (options.canSellEquippedItems ? "No" : "Yes"));
+    myDoNotSellEquippedControl.setDisplayName("Can sell used items: " +
+            (options.canSellEquippedItems ? "Yes" : "No"));
     if (myDoNotSellEquippedControl.isJustOff()) {
       options.canSellEquippedItems = !options.canSellEquippedItems;
     }

main/src/org/destinationsol/menu/CreditsScreen.java

@@ -69,15 +69,11 @@ public CreditsScreen(float r, GameOptions gameOptions) {
       {
         "Contributors on GitHub",
         "",
-        "Cervator",
-        "Rulasmur",
-        "theotherjay",
-        "LinusVanElswijk",
-        "SimonC4",
-        "grauerkoala",
-        "rzats",
-        "LadySerenaKitty",
-        "askneller"
+        "Cervator, Rulasmur",
+        "theotherjay, LinusVanElswijk",
+        "SimonC4, grauerkoala, rzats",
+        "LadySerenaKitty, askneller",
+        "JGelfand, AvaLanCS"
       },
       {
         "Soundtrack by NeonInsect"