cache both gradle and haveno-specific dependencies when running CI.
windows binaries are built using ./gradlew build directly, since
windows users have to download binaries manually regardless.
- Add mention in the README
- add new workflow label.yml, which uses github actions to post the
rules of the bounty as a comment in an issue labelled 'bounty'
- add docs/bounties.md where the bounty system is documented
* add CODEOWNERS and move file to .github/
* remove 'haveno mockups.pdf' (movedo to haveno-design) and bitcoinj-checkpoint.md
* README: add banner and update 'Status of the project'