Fix breakpoint event

Few problems:
 - we were passing a dict instead of a list of breakpoints
 - if the breakpoint had a source which was {} we crashed
 - we didn't support the 'removed' event

python3/vimspector/debug_session.py

@@ -1050,7 +1050,9 @@ class DebugSession( object ):
     if reason == 'changed':
       self._codeView.UpdateBreakpoint( bp )
     elif reason == 'new':
-      self._codeView.AddBreakpoints( None, bp )
+      self._codeView.AddBreakpoint( bp )
+    elif reason == 'removed':
+      self._codeView.RemoveBreakpoint( bp )
     else:
       utils.UserMessage(
         'Unrecognised breakpoint event (undocumented): {0}'.format( reason ),