* add selected rows supported in framework

* copy stop_gradient property in clone, test=develop

* fix pruning issue, test=develop

* fix kLookupTablePath issue, test=develop

* sync program, test=develop

* copy subblocks, test=develop

* add unittests, test=develop

* general table

* add sparse table
test=develop

* no cvm
test=develop

* add no_cvm
test=develop

* add note
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* code style
test=develop

* add key of optimizer
test=develop

* solve pslib stop core
test=develop

* barrier
test=develop

* add notes
test=develop

* add table id in cache shuffle
test=develop

* table id
test=develop

* code style
test=develop

test=develop test=document_fix

* Disable memory opt pass when DNNL is on

* Refine comment above mem optimization pass enablement

test=develop

test=develop

* test=develop, speed dense calc & communication

test=develop

* Remove self-set accuracy parameters of op tests: max_relative_error
test=develop

* fix error
test=develop

* Remove self-set accuracy parameters of op tests: max_relative_erro
test=develop

* fix error
test=develop

* add Linear layer
test=develop

* update unittest for coverage
test=develop

* Remove self-set accuracy parameters of op tests:atol
test=develop

* keep smaller parameters
test=develop

* fix error
test=develop

* fix post training quantization bug of memory constrained, support the input be different, test=develop

* add some debug flags to auto growth allocator, test=develop

* add comments about auto growth, test=develop

1. Make while_op accept GPU conditional data
2. Add more complex test cases for while_loop API

test=develop

* Remove self-set accuracy parameters of op tests: max_relative_error
test=develop

* fix errors
test=develop

*use dtype to determine whether check_grade is needed, and delete useless class

The fixed bugs:

1. The condition sub-graph is not pruned
2. When backward graph is extremely simple, the whole backward ops are pruned.

test=develop

* fix compiled error of butil when with_pslib=on and with_testing=on
* test=develop

adds unary operator __neg__ for VarBase in dygraph mode, and for Variable in static graph mode.