Make get_input() function more flexible

[axiomcura]

          Consider using the data_type string to dynamically call what are currently defined as global variable values for these blocks. Doing this might reduce the number of lines and help simplify what happens here. For example:

return (
    expand(datapaths.build_path(data_type=data_type), basename=plate_name)
    if tolist
    else datapaths.build_path(data_type=data_type)
)

Originally posted by @d33bs in #60 (comment)