Improve Manual Extraction process

Adds improvements to the manual selection process. You can now
click to lock the selection box, and can also go forward and backwards
to modify selections after they have been made. You can also now push
'Q' to skip all remaining images to quickly save the extractions you
have already made.

utils/SubprocessorBase.py

@@ -75,7 +75,8 @@ class SubprocessorBase(object):
         return None
         
     def inc_progress_bar(self, c):
-        self.progress_bar.update(c)
+        self.progress_bar.n += c
+        self.progress_bar.refresh()
     
     def safe_print(self, msg):
         self.print_lock.acquire()