make phase2 compatible with coordinator tools

[gubsheep]

Changes:

• add an optional verbose mode -v <progress_interval> option in contribute. when you pass in -v N, contribute will print a progress update to stdout every N points exponentiated. Coordinator tools reads from stdout and tracks progress.
• add <path/to/phase1/radix> as a required argument for new and verify_contribution. Coordinator tools call these binaries from different directories than the phase1 radix location.

[weijiekoh]

@kobigurk reminder to both of us that once we merge this, we should update the commit hash in section 6 of https://github.com/appliedzkp/semaphore-phase2-setup/tree/kobigurk/VDF_instructions