feat(activate): change activate to alias, promote to command

[nihonjinrxs]

Makes promote the primary command, with alias activate.

Adds option aliases for 'activate' / 'promote' command:

• from = source-environment
• from-build = build-sid
• to = environment

Adds appropriate examples showing usage.

resolves #8

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[dkundel]

Thank you for your contribution @nihonjinrxs :) it's very much appreciated!

[welcome]

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