Update for 2022

[ravn]

The following should be done:

• Revise to update dependencies. This either requires lifting Java version to 8 which is what SLF4J requires, or switching logging to java.util.logging.
• Use github actions to build sources
• Make a runnable jar as requested in #2
• Switch to markdown.
• Ensure no warnings reported by Intellij, Eclipse and optionally other checkers.