* Inception fusion operator.
* Support horizontal layer fusion in conv_fusion_op.
* Search conv algo strategy for variable-length input.
   search N times and cache the searched algos. For other input, choose the algo of input whose area is closest to this input.

* Refine conv_fusion_op for identity activation.
* Fix unit testing.
test=develop

* Convolution fusion operator.
* Clean code
test=develop