skeleton & YARD doc for cmd_suspend added

functionality untested atm.
cmd_suspend_help also added
adds suspend to meterp and adds full pid validation

This fully fixes RM7223 and adds the suspend command to the meterpreter
interface.
Suspend allows you to suspend and resume running processes on the
targethost.  It was originally written as a post module (and the dll
version will be submitted as such later), but egypt suggested I add it
to meterpreter
cleaned up at validate_pids conversion, fixed YARD doc

in validate_pids no longer need dup as conversion to ints was cleaned
up to use map.  Which also improved readability and allowed adding uniq
and compact, thanks egypt.
YARD doc on cmd_suspend was incorrectly organized
Addressed egypt's comments

-changed the suspend/resume loop logic to reduce code duplication.
-fixed up some print_*'s to remove embedded \n's
-changed formatting on some error messages
-switched comment to a TODO:
-change host_processes.select (blah} to use .find instead
-adjusted code due to remvoal of the pids.dup, resulting in arr_pids
disappearing
changed TODO to @todo per egypt
Merge branch 'rapid7' into kernelsmith-msfconsole-suspend
Cosmetic fixes

[FixRM #7223][See #1283]
Merge branch 'master' of github.com:rapid7/metasploit-framework into rapid7