(chocolatey#2500) List parameters in templates

This adds the ability for the template command to list the parameters
in templates. If the template is installed via a package, the
parameters get cached in a file called .parameters in the template's
directory. This file is ignored by calls to choco new, as it is
excluded from being copied.

There another method added to TokenReplacer to get the parameters via
regex. This keeps the regex in the TokenReplacer class.