modified in path_services

restrict path returned by PathService::Get() to be absolute path
Working on file_util && add unit test for file util
bugfix: may return reference to an un-initialized global object
add RemoveFile in file_util along with its unittest part
working on file_util
make ThrowLastErrorIf as a macro and incorporates file information etc.
add special method for streaming std::wstring
slight change in FileEnumerator ctor
add few functions for file util
wokring on file_util
replace LOG_ERROR with LOG_WARNING.
Confilicts with macro ERROR defined in windows sdk.
working on file_util
Add ReadFileToString, WriteStringToFile, and AppendStringToFile
Done with file_util
Revise AutoReset && add its unittest
add auto_reset
add document for file_util