REST API for Credentials
Overriding the registerType of RED.nodes to add a new optional parameter that contains the definition of the credentials.
It makes sense to define the credentials when defining the type if the developer want credentials support.
Automatically load the credentials
When the node is registered into the credentials API, the credentials are loaded directly in the attribute credentials.
Connecting the editor to the credential API.
I added a TODO for the validation of Credentials field.
As the other field, the developer should be able to set the credentials as required and also give a validation function.
Add Sample that use the credentials.