* change v2.0.0-beta2 to v2.0.0-rc, test=develop

* modify cpp_demo

* modify model_optimzie_tool doc

* modify FPGA and ios compiling

* fix: fix fpga_doc

* fix: doc review

* fix: fix develop/fpga md

* fix: update fpga.md

* fix: fix fpga doc

* modify source_compiling

* fix error in index

* update model_quantization.md

update model_optimize_tool in tutorial.md

* modify source_compiling

* modify source_compiling

* opt too

* modify style

* modify compiling

* modify source_compiling

* modify source_compiling

* modify source_compiling

* opt too

* fix bug and add toc

* update support_operation_list.md

* [Java API doc] add java api doc

* add x2paddle_models_doc

* modify source_compiling

* modify source_compiling

* [C++ API doc] add c++ api doc

添加对Model_optimize_tool页面中prefer_int8_kernel的说明信息

* up

* up

* up

* up

* up

* up

* up

* up

* up

* up

* up

* up

* use minima theme