Expose set<attr> methods to work correctly

[ejhernandez@…]

In dhcp module, I have found a problem which it might be solved with a new approach when setting a single attribute on a row in a model may be set.

This is the case on a form:

setDefaultGateway('eth0', default_gateway => { 'ip' => '10.0.0.1' });

As we can see, there is redundant information. We may implement a map when selector is just one element not to pass field name attribute, in the example default_gateway since it is set on the _exposedMethods definition.

[ejhernandez@…]

(In [8547]) Now you can expose a method which just setting an attribute closes #860 (spent 1)