Harmonize CLI for --force, --resume and --exists

[hannes-ucsc]

• Change --force to --upload-exists=cancel and --resume to --upload-exists=resume
• Change --exists to --object-exists
• Reintroduce --force as a shortcut for --upload-exists=cancel --object-exists=overwrite
• Change --resume as a shortcut for --upload-exists=resume --object-exists=skip

@arkal, what do you think of this?

[hannes-ucsc]

--upload-exists=discard is probably better than --upload-exists=cancel

[arkal]

I like it. Can there be a --restart in addition to --resume and --force in the mutually exclusive group which is analogous to --upload-exists=cancel --object-exists=None which is a safe option for restarting a pending upload?

[hannes-ucsc]

SGTM