Changes default offset

Points to the beginning of the block
Forgot the comment
Landing #1733, setting a sensible heapsray offset

@wchen-r7 says that nobody's using it today, much less relying on the
default, so this should make no functional difference to any browser
exploits.
Fix RM7896, global show opts has non-eval #{text}

thx to mudge for reporting & jduck for properly blaming me.
This change also causes the actual DefaultPromptChar to be displayed vs a hard coded ">"
Merge branch 'master' of git://github.com/rapid7/metasploit-framework