various changes to date fields

[simon]

​APA style uses the date for citing journal articles, but right now the journalArticle type has no date field.

It would also be nice from my standpoint if we could combine year, date, and lastModified (or at least date and lastModified) into one date field and use it on all objects.

[dstillman]

(In [476]) Closes #178, various changes to date fields
Closes #111, minor modifications to field list schema

Changes per above tickets and comments at ​http://chnm.grouphub.com/projects/310105/msg/cat/2333974/2995041/comments

• date, year and lastModified merged into date
• added date field to journalArticle
• added series, seriesTitle and seriesText to journalArticle
• added seriesNumber (along with series) to book and bookSection

[simon]

(In [479]) closes #112, ingested items should be automatically added to selected project
references #178, changes to various date fields

• updates CSL to work with the latest schema. we can now (almost) generate completely valid APA style. the only issue is that there's no syntax for specifying short forms for page and creator type labels.
• updates scrapers to use date field rather than year field.
• removes now-unnecessary translation engine code pertaining to year field.