set the correct cnn type according to the weights filename

[njuaplusplus]

Solve the loading problems mentioned in this closed issue: https://github.com/my89/imSitu/issues/3#issuecomment-469077352

Because class baseline_crf has a default parameter cnn_type='resenet_101', the eval.py will always try to load the weights to the resnet101 model. That's why other models can not be loaded correctly.