Backtrace Unity 2.1.3

This release includes updated library lists and improved packaging.

• BacktraceUnhandledException will generate environment stack trace if Unity stack trace is empty. BacktraceReport will still generate normalized fingerprint for unhandled exception without stack trace.
• BacktraceUnhandledException will provide information from Unity Error logger in source code property, which should improve error analysis in web debugger.
• BacktraceAttributes won’t try to collect Annotations anymore.
• Annotations won’t use ComplexAttributes property anymore.