auto generate `USE_OP(XXX)` in pybind.cc

[luotao1]

Currently, we should manually add USE_OP(XXX) in paddle/pybind.cc. To auto add USE_OP, we plan to generate a pybind.h file bypaddle/operators/CMakeLists.txt. For different Ops, the rules are as follows:

• net_op doesn't need any USE_OP.
• if XXX_op only has .cc file, it's USE_CPU_ONLY_OP.
• if grep 'OperatorWithKernel' XXX_op.cc is null, it's USE_NO_KERNEL_OP
• USE_NO_KERNEL_OP > USE_CPU_ONLY_OP: meas that if a op is both USE_NO_KERNEL_OP and USE_CPU_ONLY_OP, it is USE_NO_KERNEL_OP.