closes#160, cache regular expressions
closes#188, rewrite MARC handling functions
MARC-based translators should now produce item types besides "book." right now, artwork, film, and manuscript are available. MARC also has codes for various types of audio (speech, music, etc.) and maps.
the EBSCO translator does not yet produce attachments. i sent them an email because their RIS export is invalid (the URLs come after the "end of record" field) and i'm waiting to see if they'll fix it before i try to fix it myself.
the EBSCO translator is unfortunately a bit slow, because it has to make 5 requests in order to get RIS export. the alternative (scraping individual item pages) would be even slower.
regular expression caching can be turned off by disabling extensions.scholar.cacheTranslatorData in about:config. if you leave it on, you'll have to restart Firefox after updating translators.
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