TOOLS: Add GUI option to run a tool on all the files with the same extension

By default the option is ignored. It needs to be enabled on a per tool basis.
SCUMM: Enable multi-files run option in compress_scumm_san
SCUMM: Enable multi-files run option in compress_scumm_bun
KYRA: Enable multi-files run option in compress_kyra
NEWS: Mention new GUI tool multiple file option