validation: fix unrequired params being added as undefined, and value tests
validation: fix unrequired params being added as undefined, and value tests

- unrequired parameters were being added as 'undefined'
- value tests were testing against wrong variable, causing lists to
  fail isType validation
- realizing isType should probably be renamed something like
  isValidTypeAndValue or some such.

ericblade/mws-advanced,ericblade/mws-advanced