Validate all YAML against a schema

[alexdresko]

You can use xsd.exe to create an initial schema, and then tweak it by hand if necessary. Typically, the schema created by xsd.exe is close, but not perfect. https://msdn.microsoft.com/en-us/library/x6c1kb0s(v=vs.110).aspx

Would recommend adding a gulp build/watch task to do the actual validation.

[zshall]

In version 2 we're using YAML. The XML-based channel lineup will be removed from in favor of a new data schema that will be documented in the repository. Some YAML schemas and validators exist, and this issue should attempt to try making use of one, perhaps utilizing a plugin in Visual Studio Code to make sure everything is correct. Validation occurs in the app too to some extent, throwing errors if we encounter malformed configuration files.