Add support to show all pool attributes and set them.
Also add some helper functions to FieldMap to change and check the
requested attributes.
This was needed because the layer3domain needs to be set through
attributes instead of a link function (this should be changed, but for
now we will be compatible to ndcli).
So we filter out the layer3domain name and replace it with the ID, so
that the update can do both at the same time. Maybe there is a better
way to handle this in the future.
Gibheer