allow for .xls(x) DS input

[sarahcn]

Submission guide states that DS can be in either .txt or .xlsx input format - I had misread that initially and was only allowing for .txt input
maybe it's possible to have just one 'read' function that has an argument for dd=TRUE or dd=FALSE (where dd=FALSE means it's read in as a DS file)

[broomej]

I'm assuming this is about read_ds_file() and read_dd_file(). Do changes need to be made elsewhere?

[broomej]

I just noticed that dd = TRUE is an argument for read_ds_file(). Do we want to use read_ds_file() to read datasets and data dictionaries, and depricate read_dd_files?

The alternative I can think of is to leave both functions, but have them as a wrapper for more flexible function (maybe exported, maybe not, I'm not sure) that takes the dd argument. This seems maybe a little more convoluted than necessary

[smgogarten]

read_dd_file calls read_ds_file(dd=TRUE), so read_ds_file is already the base function.