add ability to do post-write hooks on a per-jurisdiction basis

[jamesturk]

in Chicago we can't know if the omnibus bills are omnibus until after we finish, likely solution is to allow people to write code that runs against the DB/models

[fgregg]

Putting some more flesh on the problem for @twneale

In Chicago, we have a lot of legislation for routine matters. Often, these individual bills get packaged into new omnibus bills. Here's an example: https://chicago.legistar.com/LegislationDetail.aspx?ID=1526672&GUID=4B542665-F6DD-4C4C-BA4B-6107DBDA8BD7

We need to model this relation of replaced-by and replaces for individual bills and the omnibus bills and vice versa. However, there is no way to tell by what type of relationship bills have just by looking at a legistar page of individual bill.

Indeed, the only way that that I can think of for identify these relations is by looking at the structure of related bills once we have seen them all and seeing which ones have many-to-one relations.

[jpmckinney]

Related #81