Addressed CodeQL warnings, fixed an unloadable input stream type

• The warnings were all related to implicit casting to long and potential over/underflows. I don't think they were practically exploitable, but I've addressed them anyway.
• Fixed a bug where UconnInputStream wouldn't load in Setup Offline at runtime (just needed an explicit default constructor).

Fixed up some unit test warnings

The changes probably don't even affect the executable .jar. I thought I'd bump the version anyway.

Updated HTML in help files to meet current standards

Just a minor documentation fixup. No content changed.

Jam v3.1.0

This release has been brought up to date with Java SE 11, and all dependencies (JavaHelp, Guice) have been brought up to date. The old Ant build script has been replaced with a more modern Maven, removing the need to keep the dependencies in the source tree.