Add DUKEMS catalogue and document type

These commits add basic configuration for the UK-EMS catalogue and a document type to fill it out. Currently the document type inherits from GeminiDocument and doesn't make any changes. One sample document and a very basic HTML viewing page are included, and so is a basic editor view to create records. I haven't included anything specifically to add fields for semantic metadata (e.g. chemical species, industry sectors). I'm not sure whether this will follow automatically based on the ongoing semantic search development work.