add warning when data-papers.yaml obj has a symbol in TYPE field

[jes089]

sometimes in the data-papers.yaml file, there is: TYPE: in-proceedings or TYPE: in_proceedings into the data-papers.yaml and bibtex are not supposed to have any symbols or spaces in the type field. so its generating @in-proceedings which isn't correct bib format.

Proposing to add a check in the data-build.py script so that it checks and outputs a warning if this happens in the future.

[bhuffaker]

That would be fine, but suspect it will be lost in all the verbose message (including many warnings) that the code already produces.