Metadata Decorators for OAI:DC and OAI:ETDMS

[mbarnett]

Context

Now that we have introduced Draper for decorators, we're setting up specialized Metadata decorators that can acts as adapters between arbitrary classes and the metadata rendering logic needed for Oaisys and ActsAsRDFable.

Changes

• Adds OAI:DC decorator for the Item model
• Adds OAI:ETDMS decorator for the Thesis model
• Adds special case to the download controller to handle downloading files whose names have spaces in them but which LAC cannot handle without removing all spaces and space-escaping.
• Tweaks Draper setup and helper registration in order to ensure consistent behaviour for decorators whether they are run by the main application or an engine.

[ualbertalib-bot]

	1 Warning
⚠️	There are code changes, but no corresponding tests. Please include tests if this PR introduces any modifications in behavior.

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[murny]

Very nice 👍. Great job on explaining the tricky pieces with well written code comments