Remaining PB on 2.0 after backport of changes on parameters

[Chabrier]

Remaining PB on 2.0:

Not working

Expe$ cvle-2.0 -P 2CV 2CV-parcelle.vpz -t ./theTemplate.csv
debug: Generates template file
Failed to generate template file: Path::operator/(): expected a relative path

Working on 2.1

Expe$ cvle-2.1 -P 2CV 2CV-parcelle.vpz -t ./theTemplate.csv
debug: Generates template file

same problem on 2.0 with regular behaviuor

mpirun -n 2 cvle-2.0 -P 2CV 2CV-parcelle.vpz -i template.csv -o restemplate.csv
block size: 5000
package   : 2CV
timeout   : 0
input csv : template.csv
output csv: restemplate.csv
workspace prefix: 
vpz       : 2CV-parcelle.vpz
worker fails: Path::operator/(): expected a relative path
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 1 in communicator MPI_COMM_WORLD
with errorcode -4.

NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.
--------------------------------------------------------------------------

Originally posted by @Chabrier in https://github.com/vle-forge/vle/issues/389#issuecomment-931380082