defines badgeClass in JSON-schema, a sample extension for age target, and a sample extended badge class that uses it
updated description to be get rid of inaccurate text I had copied in
2 spaces for tabs, renames extension object based on suggestions
adds checksum object with alg,hash properties to the badgeClass schema and its example
switched to a single field method for adding a checksum, string like alg
stubbing the beginnings of a location schema