Support PURL shorthand for all commands

[andrius-puksta-sensmetry]

Commands:

• add
• remove
• clone
• info
• env install - not sure if needed; given IRI is an identifier without any semantic meaning
• env uninstall - same as env install
• experimental (added in feat: relative directory usage type #426) - currently irrelevant, but will be

Not relevant for:

• init
• include
• exclude
• build
• publish
• lock
• index
• sync
• sources
• print-root