tag names, places, etc. in heaney group sheets

First pass at tagging names in the heaney1.xml document and linking to VIAF, GeoNames.org, or DBpedia.  A few general notes:

- I've tagged every author byline with their VIAF id; may be useful, e.g. if we pull out a single poem from the databse
- I may have been somewhat inconsistent in tagging names in titles, especially in the titles listed at the beginning of each sheet
- I have used VIAF and GeoNames.org identifiers where possible/reasonable
- there are several references to mythical persons/groups/deities, and also a few fictional persons; I tagged the first few but was very doubtful about how and whether to tag, so left the others untagged.  Please let me know how you want to handle this and I will update before you accept the pull request

Several more detail issues; I'll see if I can add comments to the appropriate line in the pull request or commit for the specific persons, assumptions, etc.