Update to latest SK and fix issues

[jasongin]

Fixes #151

• Fix a bug in the dynamic type exporter that caused it to skip exporting parameter types referenced by interface methods.
• Automatically switch to the JS thread when calling form .NET to a JS interface method.
• Emit stubs for add_ and remove_ event methods when dynamically generating a JS proxy for an interface. Events are still not yet supported, but this fix prevents events on an interface from blocking other members of the interface from being used.
• Include base interfaces (extends clause) when generating interface type definitions.
• Fix doc-comment lookup for generic methods when generating type definitions.
• Update the example to Semantic version 0.24.
  • It has been a while since the last update, so there were several API changes that required updating the example.js code.
  • It has a new way of dynamically loading the PromptTemplateEngine assembly which requires a minor workaround. That took me a while to figure out why the input string wasn't getting incorporated in the request: because when that assembly was not loaded the null prompt engine ignored the input.