Docs: Modified LAR w/ Excel

[meissadia]

File: https://github.com/cfpb/hmda-platform/blob/master/docs/ModifiedLarWithExcel.md

Update: Unrelated to combined file, this wiki needs to be updated with correct header info. Step 6-9 cover how to add a header to the modified LAR, but users can now download the file with the header included. Let's remove Steps 6-9 and add the following (in bold) to Step 1.

Navigate to the Modified Loan/Application Register (LAR) page here. Enter the institution name in the search box, and click Download Modified LAR. If you would like to include the data field heads, select the checkbox Include File Header.