Introduce new migration procedure.

This creates a new migration module that include upgrade logic files, one file for each DB version. It should be noted that this will not support downgrades (the previous method didn't really support them either)

pyfa.py

@@ -84,6 +84,7 @@ if __name__ == "__main__":
     import os.path
 
     import eos.db
+    import eos.db.migration as migration
     import service.prefetch
     from gui.mainFrame import MainFrame
 
@@ -91,7 +92,15 @@ if __name__ == "__main__":
     if not os.path.exists(config.savePath):
         os.mkdir(config.savePath)
 
-    eos.db.saveddata_meta.create_all()
+    if os.path.isfile(config.saveDB):
+        # If database exists, run migration after init'd database
+        eos.db.saveddata_meta.create_all()
+        migration.update(eos.db.saveddata_engine)
+    else:
+        # If database does not exist, do not worry about migration. Simply
+        # create and set version
+        eos.db.saveddata_meta.create_all()
+        eos.db.saveddata_engine.execute('PRAGMA user_version = %d'%config.dbversion)
 
     pyfa = wx.App(False)
     MainFrame()