MazeGenerator mazes can't be solved by discrete movement

[timhutton]

MazeGenerator uses AgentQuitFromTouchingBlockType and the goal is a vertical column of blocks. With discrete movement the agent can never actually touch the column.

[timhutton]

Suggestion: add four blocks in the floor around the base of the column. (But changes the visual appearance.)

Other fix: use AgentQuitFromReachingPosition instead. Problem here is that the maze endpoint is unknown by the quit producer, so the maze generator would have to communicate with it. Could we make MazeGenerator implement QuitProducerInterface too.

[DaveyBiggers]

Am going to add an option to the MazeDecorator which will create a quit producer for the agent (using the correct location). There will be some wrangling to get this to work, since the quit producer needs to be client side, and the maze is created server side... but I have a cunning plan, which will have to wait until next week.