Jail support for pkgng module

Add a *jail* parameter to the pkgng module that is passed as a `--jail` parameter to `pkg`. With jail support in `pkgng` it is easier to setup new jails (e.g., by making it easy to install Python into the new jail) so that the new jail can be used with Ansible in following plays.

Besides jail support some small bugs were fixed and the error reporting was improved.