Update to latest DESI-doc revisions of data files about desimodel

[sbailey]

PR #45 updates:

• desi.yaml
• throughput files, with refactoring from original inputs/throughput/DESI-0347-throughput.txt
• platescale.txt
• fiberpos.*

platescale.txt provenance: the v15 (and prior) file in DocDB incorrectly references v3. The data actually has changed since v3 (they caught a tan(theta) vs. theta bug) and the latest text file does contain the correct data, it is only the header comment that is incorrect. The version in svn that references "v14" is my fault: I "corrected" that by hand, but doing so silently does make for messy provenance. PR #45 provides more automated DocDB -> data file provenance so I've reverted to using exactly the file as it appears in DocDB without hand editing the comment.

[weaverba137]

Did the updates ever happen? Will the changes also involve changes to the data model?

[dkirkby]

PR #45 has already been reviewed and merged, so I think this issue can be closed now but @sbailey should confirm.