No ability to save/read disabled status for controls to/from input file

[LRossman]

PR #751 added API support for disabling or enabling simple controls and control rules, with the default state for new controls read from a file or created by code being enabled. If a control or rule status is changed to disabled in code there is no ability to save this condition to an input file nor to read from an input file that a control or rule should be disabled.

I propose that we add the label DISABLED (or perhaps INACTIVE) to the start of a simple control statement or to the end of a rule's statements to indicate that the control or rule should not be enabled.