Update pql.markdown
Update pql.markdown

Clarify function support.
puppetlabs/puppetdb,kbarber/puppetdb,senior/puppetdb,waynr/puppetdb,rbrw/puppetdb,mullr/puppetdb,puppetlabs/puppetdb,waynr/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,mullr/puppetdb,kbarber/puppetdb,kbarber/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,senior/puppetdb,mullr/puppetdb,waynr/puppetdb,mullr/puppetdb,puppetlabs/puppetdb,senior/puppetdb,waynr/puppetdb,mullr/puppetdb,rbrw/puppetdb,kbarber/puppetdb,senior/puppetdb