used the flag "opt_level" to control GraphKernel,
0 means disabled while non-zero value means enabled.
the default value is controlled by context "enable_graph_kernel",
but if it's also set in "graph_kernel_flags", then the flag will prevail.

supported the whitelist and blacklist operators for GraphKernelExpander.
"enable_expand_ops", "enable_expand_ops_only", "disable_expand_ops".

If the ENABLE_DUMP_IR is off, the program will raise ValueError to
remind user to turn on ENABLE_DUMP_IR.

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'.