Create dai-author-date-alpha.csl

A preliminary attempt at a Deutsches Archaeologisches Institut bibliographic citation style, according to the manuscript guidelines provided here: http://www.dainst.org/it/node/28770?ft=3. While most of the style seems to work reasonably well, there are still some minor problems, especially with punctuation, that I have not yet corrected. Use at your own risk and check carefully.