Changed default value of the IPv6 address parameter to undef so that we don't get address6 set in a host definition to an IPv4 address that facter returns.
Added rendering of the address6 value, if the parameter for an IPv6 address is set.
Added a subsection for object defined type usage.
Added a subsection for the icinga2::object::host defined type's usage.
Added a note about IPv6 addresses in host object defined types.
Added rendering of vars; removed it from the list of parameters that need to be added.
Removed groups from the list of needed parameters in the host ERB template since the groups variable is already getting rendered.