FOFFormFieldRules::getInput

At the timing of this writing (2013-12-03), the Joomla "rules" field is buggy. When you are dealing with a new record it gets the default permissions from the root asset node, which is fine for the default permissions of Joomla articles, but unsuitable for third party software.

We had to copy & paste the whole code, since we can't "inject" the correct asset id if one is not found. Our fixes are surrounded by `FOF Library fix` remarks.