Updating core sdk to V1.2.0 & fixing XML comments for better intellisense support
Adding missing XML doc file in sample
Updating web.config to use mode based API endpoint configuration
README cleanup
  - Moving NuGet installation instructions to wiki
  - Adding SDK configuration instructions
Fixing missing applicationId in config section
Adding custom configuration support for IPN messages
updated developer account email
updated stubs, Changelog.txt and version for 100 release