implement caching and hashing #2

this PR mainly revises the algorithms for the functions that iterate over each item in a collection, and the functions that add documents to the search index.

the main changes to the functions iterating over each item in a collection:

~~better checking of pre-existing items~~

~~using sets to determine old/new/existing records~~

the main changes to the functions adding documents to the search index:

~~checking for existing version of document before adding~~

~~better logic to check/know when to check for another record~~

other minor changes:

~~comments/docstrings~~

~~updates to search.html template~~

this is ready to go, except for the fact that... it doesn't actually use hashing yet. we're at 16 commits, all helpful to making this tool more functional. but we should still squeeze in hashing before we merge this.

import hashlib

hashlib.md5(u"hello world".encode()).hexdigest()

more details... fixing alert boxes for control panel... so I got that goin for me

Aright forget about hashing content, just re-index everything. We'll come back to hashing soon.