Pull metadata info from metadata-asset-tracking-tool repo

[jacobdadams]

With the first draft of the Metadata project nearing completion, this will let us use that in our current Auditor process. By using the MATT repo instead of the internal SDE metadata, we'll remove the arcpy dependency and enable auditor to be run from anywhere.

• Class to represent a layer's metdata (SGIDLayerMetadata)
  • Classes to hold individual chunks/groups of chunks of markdown
    • Ignore/remove/strip comments
  • Basic structure, simple case
  • markdown -> HTML conversion
  • Schema
  • Ability to add common pieces (CC license, disclaimer, shelved text shelved/static notes will be added as part of the auditor process instead of the class itself as they refer to AGOL-specific concepts instead of general concepts applicable to all metadata)
• Class for storing pygithub ContentFile representation of files (MetadataFile)
  • Methods for parsing ContentFiles into SGIDLayerMetadta obejcts
    • Parsing schema
    • Combining county-specific parcel/LIR data with common data
• Class to hold MATT repo contents (MetadataRepoContents)
• Figure out how to compare AGOL description with one from SGIDLayerMetadata (AGOL adds some formatting/nofollow ugc tags to hrefs)
• Prototype SGIDLayerMetadta -> AGOL Item elements
• Update checks and fixes to incorporate data from MATT