Add bemanify-org.py script for automation at org level

[neatudarius]

While working at bemanproject/beman#159, I discovered how handy is to have a script which does an operation on all repos in org.

Features:

• do fork all repos in bemanproject org
• clone all forks
• sync fork and checkout to origin/master
• keep current status of each repo (assume default branch is used); do checkout to a provided branch, add files with a provided commit message, push branch, generate a link with a PR

[neatudarius]

WIP, I have a Bash script which helps me in bemanproject/beman#159, I'll switch to Python or Rust at some point. This should not be useful for a large set of people, so I think we can use Rust here.

@JeffGarland , I still regret tidy is not written in Rust...