better handling of p() results for non-scalars

will now return all values of an arrayref in array context
will now return all keys of a hashref in array context
(still returns the ref itself in scalar context)
can also now specify "*" as a part of a composite key
for instance: `p("Reservations.*.Instances")` returns just the instances of all the reservations
-	returns them as an array in array context
-	returns them as an arrayref in scalar context
example:
-	aws ec2 describe-instances | jsonp 'say $_->{PublicDnsName} foreach p("Reservations.*.Instances")'