Add packagedata to cellmaps_vnn which creates an RO-Crate with training and or test data

[coleslaw481]

Add a new mode to cellmaps_vnncmd.py under packagedata branch that does the following:

-- Takes same inputs as train mode and copies that data into an RO-Crate in a standard structure where each file has a label on the column name.
-- Includes new flag --omitscore that omits the prediction value from the training file.
-- Includes a readme describing format of each file along with source
-- Requires information about source of each training file