Rename a lot of files

* about_dialog -> AboutDialog
* bb_editor -> BBEditor
* export_project_dialog -> ExportProjectDialog
* setup_dialog -> SetupDialog
* string_pair_drag -> StringPairDrag

src/tracks/SampleTrack.cpp

@@ -41,7 +41,7 @@
 #include "AudioPort.h"
 #include "SamplePlayHandle.h"
 #include "SampleRecordHandle.h"
-#include "string_pair_drag.h"
+#include "StringPairDrag.h"
 #include "Knob.h"
 #include "MainWindow.h"
 #include "EffectRackView.h"