Fix formatting for YAML, move Wiki link up

The link to the Wiki authoring guidelines was so buried in the text that I skipped it and filed a few issues complaining about a lack of information (e.g. #573, #574).

I've Marked Down properly the YAML section example, and replace the old Chart with the [reference metadata](https://github.com/telerik/kendo-docs/wiki/Directory-Structure-and-Metadata) YAML section.