Improve documentation

Define a virtual module which consists of one or more other modules, for failover or

load-balancing purposes.

##### `name`

##### `submodules`

Provide an array of submodules which will be loaded into this virtual module. Required.

##### `type`

Select the type of virtual module from `redundant`, `load-balance`, `redundant-load-balance`

or `group`. See [virtual modules](http://wiki.freeradius.org/config/Fail-over#virtual-modules)

and [load-balancing](http://wiki.freeradius.org/config/load-balancing) for more details.

```puppet

# Load virtual module myldap

freeradius::virtual_module { 'myldap':

  submodules => ['ldap1', 'ldap2'],

  type       => 'redundant-load-balance',

}

```

yields

```

redundant-load-balance myldap {

	ldap1

	ldap2

}

```

## Limitations