Fall back to WARP if D3D11 hardware isn't present. Closes #121

* If hardware support for feature level 11 isn't present, fall back to
  the WARP software rasterizer. This will support everything needed, but
  it certainly won't run well.
* There are loud warnings - I added a debug message to the debug errors&
  warnings window so the status bar will indicate that, and it's in the
  title.
* At most once every 3 weeks there will also be a message box pop up
  when loading a log, to remind the user so that it isn't forgotten, as
  for obvious reasons this is not the intended use-case (hopefully once
  per 3 weeks isn't too often to be annoying).

renderdocui/Code/Core.cs

@@ -512,6 +512,20 @@ namespace renderdocui.Code
 
             Thread.Sleep(20);
 
+            DateTime today = DateTime.Now;
+            DateTime compare = today.AddDays(-21);
+
+            if (compare.CompareTo(Config.DegradedLog_LastUpdate) >= 0 && m_APIProperties.degraded)
+            {
+                Config.DegradedLog_LastUpdate = today;
+
+                MessageBox.Show(String.Format("{0}\nThis log opened with degraded support - " +
+                                                "this could mean missing hardware support caused a fallback to software rendering.\n\n" +
+                                                "This warning will not appear every time this happens, " +
+                                                "check debug errors/warnings window for more details.", logFile),
+                                "Degraded support of log", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
+            }
+
             m_LogLoaded = true;
             progressThread = false;
 

renderdocui/Code/PersistantConfig.cs

@@ -95,6 +95,8 @@ namespace renderdocui.Code
         public bool CheckUpdate_UpdateAvailable = false;
         public DateTime CheckUpdate_LastUpdate = new DateTime(2012, 06, 27);
 
+        public DateTime DegradedLog_LastUpdate = new DateTime(2015, 01, 01);
+
         public bool AllowGlobalHook = false;
 
         public void SetupFormatter()