(docs) Correct documentation of count() wrt matches and empty string
(docs) Correct documentation of count() wrt matches and empty string

The documentation did not include that empty-string are not counted.
It also stated that a "match" was made with the second argument when it
is an equals operation.
HelenCampbell/puppetlabs-stdlib,puppetlabs/puppetlabs-stdlib,DavidS/puppetlabs-stdlib