2. Add crop layer unitest
3. Fix bugs

2. Make SwitchOrderLayer support for softmax activation
3. Fix bugs

1. Add switch function for switching image dimensions order
2. Add CpuMatrix::backwardSoftmax function
3. Add pixel softmax layer, python wrapper and grad_test

1. change configure content to 'axis, offset, shape'
2. add an optional input to crop layer as cropping reference

1. change configure content to 'axis, offset, shape'
2. add an optional input to crop layer as cropping reference

Add the use_nnpack parameter in ExpandConvLayer, so that the convolution calculation can be switched to the NNPACK function.

Fix #2567

Modify the arguments description of ConvFunctionBase. And add the definition of backward input and backward filter function.