Update the elastic_load task to delete a bill (including version number) before indexing

[aih]

We don't want duplicate bills indexed. So before indexing a bill (e.g. '116hr200ih'), we delete the bill from the index -- if it already exists -- and then index it. We want to make sure that this affects only the same version, since we want to index various versions of the same bill (e.g. '116hr200ih', '116hr200eh', '116hr200enr', etc.)

[aih]

Solved this (I hope) by adding an id to the document during indexing that corresponds to the bill number. Then Elasticsearch will automatically update the document index instead of creating a duplicate.
(fc3464 did this in common/elastic_load.py)