use ncnnoptimize to optimize model

the typical usage

ncnnoptimize mobilenet.param mobilenet.bin mobilenet-opt.param mobilenet-opt.bin 65536 

operator fusion

• batchnorm - scale

• convolution - batchnorm

• convolutiondepthwise - batchnorm

• deconvolution - batchnorm

• deconvolutiondepthwise - batchnorm

• innerproduct - batchnorm

• convolution - relu

• convolutiondepthwise - relu

• deconvolution - relu

• deconvolutiondepthwise - relu

• innerproduct - relu

eliminate noop operator

• innerproduct - dropout

• flatten after global pooling

prefer better operator

• replace convolution with innerproduct after global pooling