kbase::file_path initial
kbase::file_path add FilePath::DirName()
kbase::file_path add some comments
file_path: add FilePath::BaseName()
file_path: add GetComponents
file_path: add EqualDriveLetterCaseInsensitive and operator== and operator!=
string_util: 1.change comments foramt. 2.add StringToLower(Upper) 3.add string case-insensitive comparison operators
file_path: let EqualDriveLetterCaseInsensitive compare whole string in case insensitive mode
string_util: * StartsWithT and EndsWithT use new case-insensitive comparison
file_path: + operator<
file_path: 1.+ function Append 2.+ function AppendRelativePath
file_path: 1.+ function IsParent 2.* checks null-terminator existence when constructs from a raw string
add functions and comments

1.add exposed interface IsAbsolute() and its internal implementation IsPathAbsolute.
2.add annotations for function IsParent() and operator== and operator!=
string_util: add functions and conversion ulities

1. + IsStringASCII for both std::string and std::wstring.
2. + ToUnsigned<T> utility struct for converts a stringT::value_type value to its unsigned counterpart.
sys_string_encoding_conversions: add functions

1. + ASCIIToWide() functions for converting a string object that contains only ASCII characters to a corresponding wstring object
file_path: add argument validation and function

1. + AppendASCII() for convenience
2. + argument validation for some functions. if validating failed, function throws an invalid_argument exception. the newly added code is executed only in NDEBUG mode
file_path: adds extension-related functions

1. + Extension() for getting extention
2.+ RemoveExtension() to remove extention
3.+ StripExtension(). same as above, but does strip on a copy
4.+ InsertBeforeExtension(). add some string after file name portion but before extension
5.+ AddExtension()
6.+ ReplaceExtension()
7.+ MatchExtension()
file_path: add public comparison functions

1.+ CompareIgnoreCase()
2.+ CompareEqualIgnoreCase()
file_path: add separator-related functions

1.+ EndsWithSeparator()
2.+ AsEndingWithSeparator()
file_path: add ReferenceParent()