wrapper in the prepare_inputs.py for executing zarp
additional options added:
--execution_env (allowed values local or slurm or none for now)
--snakefile_path path to the snake file
--bindings paths to be included in the singularity
--cluster_json path to the cluster.json (used in the slurm run)
Fixed also a test_zarp_wrapper test (this needs to be refactored and be merged with existing tests)
Fixes #130 (closed)
