Move over remaining issues from trac

[hns]

So we're going to start using github's issue tracking system. This means we need to bring over open issues from trac. We might want to do a shakeout and reexamine or reformulate existing issues along the way.

Here's a full list of issues on the Helma trac:
https://dev.helma.org/trac/helma/report/6

And of course, keep those new issues coming.