Added support for Mantis Bug Tracker

- Implemented part of MantisConnect SOAP API trough object model to avoid "hacking" SOAP Envelops and manual XML serialization/deserialization/parsing/exception processing. 

- Updated configuration tools to support Mantis

- Included patch for nusoap.php file in Mantis that fixes bug when parsing SOAP exception from .NET client as discussed at http://sourceforge.net/p/nusoap/discussion/193579/thread/9a5aff36/
This is optional, but helps you to see real SOAP exception when invalid request is made.