Deprecate the validation_{class name}_{submit field id} and validation_{class name}_{submit input id}

[michaeluno]

I'm going to deprecate the validation_{class name}_{submit field id} and validation_{class name}_{submit input id} filters for the submit field type as it is confusing with the other submitted fields.

To determine which submit button is pressed, instead I'll add the following action hooks:

• submit_{class name}_{submit field id}
• submit_{class name}_{submit section id}_{submit field id}
• submit_{class name}_{submit input id}

Then the field id can be used for all the fields, not restricted to the submit field type.

• validation_{class name}_{section id}_{field id}
• validation_{class name}_{field id}

[michaeluno]

Done in some of the following commits:

• ae660af
• 9eff6af
• d3f1bde
• dbb8220