Revise dp_make_params

[leslem]

Make sure there's actually a good use case for this. I don't see any use of this function in our existing daap repos.

Rename the function to something more relevant, e.g. get_dp_repo_params.

Fix the way that legacy repos are detected. Right now it checks for existence of board_alias argument, but this is wrong on its face, since migrated LabKey daaps still have board_alias.