Copied DynamicAggregateExportProvider over from ISIS. Wrapped with NancyExportProvider. This new one rewrites ImportDefinitions into ZeroOrMore, to prevent failures on conflicts. Right now it just picks the first one back. Which is probably okay. Also, Import and ImportMany are now inferred to allow defaults. This seems to meet the expectations of Nancy better.

Need to prioritize lookups of duplicates in accordance with how Nancy currently operates.
Ignores.
More ignores.
Move files around.
Delete.