Use templates for batch scripts

[al-rigazzi]

Description

Templates should be used by _write_xxx_script methods.

Justification

Currently, batch scripts are written programmatically, line by line, in Step functions such as _write_sbatch_script. The usage of templates would be more indicated, as the content of such scripts is pretty standard.

Implementation Strategy

Templates should be used to replace the current line-by-line functions.