Added ability to create new DBC files from the DBC file manager,

hooked up ability to change associated bus for DBC files.

dbchandler.h

@@ -86,6 +86,7 @@ public:
     int getFileCount();
     DBCFile* getFileByIdx(int idx);
     DBCFile* getFileByName(QString name);
+    int createBlankFile();
 
 private:
     QList<DBCFile> loadedFiles;