Revised description of catalog required fields
Remove "common core" term for consistent language

"common core" seems to refer to the core vocabulary of terms, but that
concept is already covered by "schema" so "Common core metadata schema"
seems redundant to me and "Project Open Data Metadata Schema" seems
like a more accurate and descriptive way to refer to this.
Clarify accessURL use with “restricted public”
re-organized changelog 

by required, required-if-applicable etc
Add detailed sub fields for publisher
Consistent use of IANA Media Type references
Style warning message
More consistent formatting for field references
Consistent use of "Yes, if applicable"
Update metadata changelog
Better language for non-licenses
Merge remote-tracking branch 'upstream/metadata-v-1.1' into gh-pages