AUP3: First round of updates

!!! THERE WILL NO DOUBT BE BUGS !!!

This is a big one and there's still several things to
complete. Just want to get this in the wild to start
receiving feedback.

One big thing right now is that it will NOT load pre-aup3
files.  An importer is on the way for that.

src/import/Import.cpp

@@ -785,7 +785,7 @@ bool Importer::Import( AudacityProject &project,
       }
 
       // Audacity project
-      if (extension.IsSameAs(wxT("aup"), false)) {
+      if (extension.IsSameAs(wxT("aup3"), false)) {
          errorMessage = XO(
 /* i18n-hint: %s will be the filename */
 "\"%s\" is an Audacity Project file. \nUse the 'File > Open' command to open Audacity Projects.")

src/import/ImportRaw.cpp

@@ -24,7 +24,6 @@ and sample size to help you importing data of an unknown format.
 #include "../Audacity.h"
 #include "ImportRaw.h"
 
-#include "../DirManager.h"
 #include "../FileFormats.h"
 #include "../Prefs.h"
 #include "../ShuttleGui.h"

src/import/ImportRaw.h

@@ -15,7 +15,6 @@
 
 class TrackFactory;
 class WaveTrack;
-class DirManager;
 class wxString;
 class wxWindow;