Merge branch 'ntark-master'

Attempt to fix appveyor publish

Revert to string.Empty for XML serializers

Fix #264 - Handle null example in IMultipleExamplesProvider<>

Try fix appveyor build

Update test projects too, oops

Version 10.0.0

PR review

Fix SecurityRequirementsOperationFilter

Re-add XML serializing

Fix all tests

Fix example tests

Fix request example

Revert to using Newtonsoft in tests

Fix compiler errors in tests