urlstring testing/enhancement

[Chad Yates]

I built urlstring testcases this weekend. Here are the test cases performed:
  URLStringTest.testBinaryBase64EncodeDecode ...
  URLStringTest.testStringVersion ...
  URLStringTest.testTypicalUrlEncodeDecode ...
  URLStringTest.testTypicalTextBase64EncodeDecode ...
  URLStringTest.testSimpleTextBase64EncodeDecode ...
  URLStringTest.testComplexTextBase64EncodeDecode ...
  URLStringTest.testPaddingPerfect ...
  URLStringTest.testPadding1Short ...
  URLStringTest.testPadding2Short ...

I also added Base64 functions that take std::string arguments for the encode
output and the decode input.  I don't know where the line is supposed to be
relating to string usage as I see most of common c++ is char* based, but
there seems to be std::string usage in some classes.  personally I like
having it as an overload option.  I can post diffs showing the new functions
if they are wanted.

,Chad