Docs section "IV.1. Spack view"

[dennisklein]

Currently we ask the user to type a somewhat longish command line in "IV.1. Spack view". We should

1. unify the command for macOS and Linux, and
2. come up with a way to make this command line shorter and more convenient to use.

[ChristianTackeGSI]

spack related, moving to "next".