* fix conflicts

* fix kernel registry realted bugs test=develop

* enable softmax op and add unit test

* move softmax sub-functions to softmax.cc, and move basic math functions to funcs.h

* migrate several ops:
  mean,
  mean_grad
  fill_constant
  square_grad
  elementwise_sub_grad
  mul_grad

* add sdg_op

* fix kernel platform registration issue

* code cleanup

* fix platform typo

test=develop

load_model
add scale, mul Op

and #pragma once in edited headers

add #include<string> in edited headers

test=develop

* link IR graph to analysis graph

* add clean code and update

* add infer_clean_pass

* add ir_pass_manager

* support fc fuse executation

* fix ir circle

Reduce one level of inheritence.

add doc

* Use Builder Chain to decorate new builders. It is easy to extend
  builders.
* Make graphviz path as a build strategy, not a FLAGS.