libioc should support iocage's template jails

[sonicaj]

Libiocage does not right now support iocage's template jails. This commit introduces the following changes:

1. Make sure that libiocage is able to create jails from iocage's template jails
2. Libiocage is able to list iocage's template jails
3. A bug fix in JailConfig where we try to fetch the rc_conf file when the jail does not exist
4. Bug fixes in special properties ( DefaultRouter, Resolver ) where a bug in libiocage did not anticipate that objects of these special properties could be sent as as set value