Update the v2 endpoint information

[mmarcotte]

As a consumer of the v2 API, so that I can have the most accurate information in my system, I need endpoints to include the information that they promise and I require.

The JSON that we supply is not exactly what we are promising in the v2.yml documentation. When talking with the IRS, who is the consumer of this API, we have decided to make a few corrections.

1. remove caseCaption from the v2.yaml for a DocketEntry
2. remove the docketNumber from the v2.yaml for a DocketEntry
3. add filedBy to the case JSON for a DocketEntry
4. add documentTitle to the case JSON for a DocketEntry