Fix max memory counter.

Fix algo. I added a todo. I'll make other comments in the PR.

Add TensorConstant check in check_node_state method.

refactor test and print the line to check with the expected answer.

increase the complexity of test.

1. remove compute_map.copy from vm.py
2. add new compute_map in compile.py
3. make code more simple

1. remove global variables
2. modify discription
3. use new way to track order

1. compute_map reset process in min_memory_generator

1. use cpmputed_map as a argument for min_memory_generator.
however which it will works remains doubt, the question I will email Fred, and Arnaud

1. Simulate execution step in generator.
2. Use new memory usage counting method

thx to Fred

1. make global variables correctly
2. use fgraph.apply_nodes replace the previous fgraph.nodes

the error is mainly caused by the check node is not work well

in previous version the memlist will store the current_mem if it's 0, but we don't need that value, so I just remove it.