Preserve properties when changing runitem datatype or suffix

[marcelzwiers]

Contrary to the attributes, in which the value are taken fro the data, the properties are user set, so they should be preserved in the same way as the bids entities are.

To reproduce run:

bidsmapper bids_in bids_out -t bidsmap_bids2bids -p nibabel2bids

Then cange some datatypes or suffixes in the bidseditor, and run:

bidscoiner bids_in bids_out

Now you get errors like:

ERROR | Skipping unknown run: [Nibabel]                                                                       
         /project/[..] 
         -> Re-run the bidsmapper and delete /project/[..] to solve this warning