Better error message for port conflict

[dmcassel]

If you bootstrap with a port that is already in use, Roxy vomits a bunch of hard-to-read error text. Detect the error and produce an easier-to-read message.

[peterskim12]

Change error reporting to simply print out value of error:format-string/ to stdout and refers user to MarkLogic error log:

Bootstrapping your project into MarkLogic on localhost...
ERROR: ADMIN-PORTINUSE: (err:FOER0000) Port is currently in use
See MarkLogic Server error log for more details.
ERROR: ... Bootstrap FAILED