only show snaps from last 30 days.
attach snaps directly to products (no Metric objs).
metric objects made in item @property method.
add mendeley_discipline attr to product.
Merge branch 'core-to-webapp' of github.com:total-impact/total-impact-webapp into core-to-webapp
adds product.host and product.genre.

largely ports Core's old genre code. move biblio parts of
that to the biblio object though.