1. Use 'const' for member functions that do not modify member variables
2. Use the 'override' keyword when overriding virtual functions

MS_RDR_ENABLE should be in {0, 1}. if it is set as other value, it will
be 0 and WARNING information will be printed to tell user.
The settings in config file set by the user takes precedence over the
environment variables. If 'rdr_enable' is 0 in environment variable,
and then 'enable' is true in config file, the RDR will turned on.

1. move common function to base recorder
2. add UpdataRdrEnable() for recorder manager, and update once
3. add delimiter virable for base recorder, set it as '.'
4. modify recorders to use the suffix parameter of GetFileRealPath()
5. improve the text in ms_context

Can not add RdrEnablePlatform because linux is supported only.
If os is linux, (!is_rdr_supported && rdr_enable) will be false always,
else, (is_rdr_supported && !rdr_enable) will be false always.

1. add env_config_path for ms_context
2. add EnvConfigParser to parse config
3. add in CMakeLists
4. clang-format, cpplint
5. fix spelling in ms_context

Use EnvConfigParser in the constructed function of base_recorder,
when a recorder is initialized, its direcctory will be set as the
value from config file. In addition, recorder_manager will get the
'enable' from config file. If 'enable' is true and the path is not a
valid value, it will be the default value: './rdr'.