Altered interface to LogSink to hide implementation of boost:regex (now using std:string)

Altered interface to LogSink to hide implementation details of boost:regex. The regular expression text is now passed as a std:string and returned as a std:string.

This was a potential portability issue and was causing VS2008 intellisense to stop working.

Testing - code compiles without error on Win 7, 64 bit using VS 2008.