string_util: add RemoveChars
string_util update src file and add ReplaceSubstrHelper
string_util: add ReplaceSubstr series
string_util: add TrimString series functions
string_util: add ContainsOnlyChars
string_util: add StringTo*CaseASCII functions
string_util: add StartsWith and EndsWith functions
string_util: add WriteInto function
string_util: bug fix WriteInto reserved memory size
string_util: add Tokenize
string_util: add JoinString
string_util: add MatchPattern
modify author copyrights