Rename allow_override_cpp to allow_hide_cpp.
Rename allow_override_cpp to allow_hide_cpp.

Reason:
In CLIF world, this parameter allows python program to define a python flag with a same name to a c++ flag. But by doing so, it will hide the c++ flag from python. (You cannot read/write the c++ flag, command line arguments won't affect it either)

Also allow_override_cpp is too similar to allow_override. The later could be used in the SWIG world, to re-define a python flag. And that flag will override the c++ flag's default value, and command line arguments will affect its value too. This is different from CLIF's behavior.

allow_hide_cpp communicates this better.

	Change on 2016/09/08 by yileiyang <yileiyang@google.com>

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=132603494

google/python-gflags