Export high scores to message base with "export" command-line option

A periodic (e.g. weekly) digest of high scores posted to SYNCDATA
will allow BBSes to have an accurate list of global high scores
without requiring the retention of several years of SYNCDATA messages.

Also, made the necessary changes to allow:
'jsexec minesweeper.js export' (for testing, primarily)

When posting an exception report, post from sysop if user.alias is undefined.

Incremented revision to 2.15 (though there were no game-play changes).