* docs build into user-specific directory so they're not a problem
with not including this in the distribution.
* misc doc improvements
* renamed handin-server.ss to main.ss
* basic operation is fine with v4
svn: r8716
* rename `current-run-status' -> `set-run-status'
* coverage should work fine with non-textual submissions
* added `current-error-message-tweaker', "checker.ss"-based checkers now use it
to show which expression caused an error ("handin-server.ss" uses
`tweak-error-message'). (This feature is a hack, and currently undocumented)
svn: r5415
