* add post training quantization demo, test=develop

* update, test=develop

1. Fix format of arguments
2. How to get model size
3. Add FAQ for compress other model

* fix some configs

* fix doc

* fix fc prefix name

* fix resnet prefix

* fix data path

* fix quantization doc 

Update PaddleSlim LightNAS

* add distillation demo and doc

* add classification quantization demo

* Add pruning demo for classification

* minor fix

* add getting ops from program

* add obtaining op params from paddle program

* add code reusage of light_nas_space

* add comments to get_ops_from_program

* add comments to get_ops_from_program

* fixed bugs

* add get_all_ops

* add get_op_latency

* add platform parameter for get_op_latency

* add get_all_ops

* add get ops from shortcut and se

* bug fixed

* fixed bugs

* add refined code

* bugs fixed

* useless test codes and op files removed

* modifying 7 to length of searched bottlenecks

* bugs fixed

* add softmax op in get_ops_from_program

* remove resize ops in get_ops_from_program

* add get_op_latency from paddle-mobile and modify getting fc op params

* add fc op params

* add batch norm in light_nas_space

* bugs fixed

* update light_nas_space: add get_model_latency

* bug fixed

* bug fixed

* bug fixed

* update get_latency_lookup_table

* add bias of fc layer in get_all_ops

* add docs for light-nas with latency

* update doc for light-nas

* add first part of method descriptions for light-nas based on android and ios

* add descriptions for lightnas basd on android and ios in demo and usage and modify get_latency_lookup_table

* fix errors in usage.md

* fix errors among the contents of android system in usage.md

* fix errors among the contents of ios system in usage.md

* add descriptions in demo.md about lightnas based on android and ios

* add auxillary methods for generating bin files and .a files for op latency test

* add links for latency estimation tools

* minor fix in usage.md

* minor errors fixed in usage.md

* update LightNAS usage

* update docs

* update get_latency_lookup_table.

* add information for get latency lookup table

* add current searched models and their corresponding accuracies for android and ios systems

* bugs in fc_op_prams are fixed in get_ops_from_program.py test=develop

* update docs

* update docs

* update docs

* update PaddleSlim results

* add more lr_strategy

* update docs

* update PaddleSlim results

* update docs

* minor update

* minor update

* modify get_latency_lookup_table.py to make it compatible for python2 and python3; modify usage.md to update the information of PaddleMobile to Paddle-Lite

* minor update to be compatible for py3

* modify get_latency_lookup_table.py to make it compatible for python2 and python3

* convert float number in get_all_ops to int number in order to make it compatible for both python2 and python3

* remove print in get_latency_lookup_table.py

* update docs

* fixed bugs in get_all_ops

* fix merge conflicts

* fix merge conflicts

* Add demo for pruning mobilenet-ssd.

* Remove unused option.

* Use soft link instead of copying files from PaddleCV/ssd