Add iDAI.gazetteer

[rybesh]

Add the Deutsches Archäologisches Institut's iDAI.gazetteer to our set of gazetteers. This is necessary for adding the DAI's version of the Getty AAT periods.

[rybesh]

The full gazetteer has hundreds of thousands of records, so we probably only want the ones necessary for the AAT periods.

[rybesh]

iDAI.gazetteer API documentation