Added GTA V folder check to main entry point in Program.cs, improved folder selection dialog

- Added bool app setting for remember GTA folder (vs. prompt every start)
 - Added checkbox to folder selection dialog for remember GTA folder
 - Changed folder selection dialog to fixed dialog window border
 - Set default Enter/Esc buttons on folder selection dialog

Program.cs

@@ -14,6 +14,12 @@ namespace CodeWalker
         [STAThread]
         static void Main(string[] args)
         {
+            // Always check the GTA folder first thing
+            if(!GTAFolder.UpdateGTAFolder(Properties.Settings.Default.RememberGTAFolder))
+            {
+                MessageBox.Show("Could not load CodeWalker because no GTA 5 folder was selected. CodeWalker will now exit.", "GTA 5 Folder Not Found", MessageBoxButtons.OK, MessageBoxIcon.Stop);
+                return;
+            }
 
             bool menumode = false;
             bool explorermode = false;