(PUP-2426) Add missing fields to environment http json

This adds the two new properties environment_timeout, and config_version
to the returned settings properties.
The timeout is either an integer measured in seconds from min 0, or
the string 'unlimited'.
Merge pull request #2757 from hlindberg/PUP-2426_add-missing-setting-to-environment-listing

(PUP-2426) Add missing fields to environment http json
Merge branch 'master' of https://github.com/puppetlabs/puppet