Rename `sourcefile` and `sourceline` to `file` and `line`

The resource endpoint was using the terms `sourceline` and
`sourcefile` to reference the manifests; other places in
the API were simply referring to these as `line` and `file`.

This commit changes the names to be consistent (`line`, `file`)
for v3, while ensuring that the old names still work properly
on the older versions of the query API.
Use `clojure.set/rename-keys` instead of doing it the hard way
Another `clojure.set/rename` cleanup, plus fix a duplicate test
Add better tests for old vs. new file/line field names

This commit adds some more rigorous tests to make sure that the
old sourcefile/sourceline field names work in v1/v2, and not in
v3... and also that the new field names work in v3 but not in v1/v2.

Also fixes some bugs that were making all three versions of the
endpoints be a bit more toleratnt of those field names than
they should be.
Merge pull request #651 from cprice404/maint/burgundy/PE-1101-make-file-line-name-consistent

Rename `sourcefile` and `sourceline` to `file` and `line`