Implement a pipeline that deploys an executable JAR

This PR adds a pipeline that runs whenever a tag of the form encyclopedia-* is pushed to the repo (as you do in the current release process). This build will run all tests and create an executable encyclopedia JAR, which is then uploaded to the repo's Downloads section.

Before merging this, you must set up the necessary variables for the username/password used to upload the JAR to the repo (or the upload step will fail). Specifically, follow the instructions at https://support.atlassian.com/bitbucket-cloud/docs/deploy-build-artifacts-to-bitbucket-downloads/ to create an "app password" and then set up the BITBUCKET_USERNAME and BITBUCKET_APP_PASSWORD variables in EncyclopeDIA->Settings->Pipelines->Repository Variables

After this change, the release process will be largely the same, but the JAR(s) built on your local machine by increment_version.sh will no longer have to be uploaded manually. You will continue to manually execute the script, push the changes/tag, and (optionally) update the project wiki/landing page and current_version.txt (this process is also documented on the wiki). In the future we can add automation for these further steps, depending on your goals and priorities.