Idle facility

Description
Hosts may be configured to disconnect sessions after a period of inactivity. The x3270 family supports an idle facility as a way to keep these sessions connected.

The idle facility automatically executes a set of actions when sufficient time has expired since the last interactive action.

Both the actions and the timeout are configurable through resources:
 * idleTimout defines the timeout period.
 * idleCommand defines the actions to run.
 * idleCommandEnabled controls whether the idle facility is enabled.

Drawbacks
Note that the idle facility is at best an imperfect mechanism, because there is no action that makes the host believe that the session is active that is also guaranteed to be harmless. For example, the Enter action is generally harmless, unless the user has entered half a command line and then been called away from the terminal. For this reason, there is no support for the idle facility in wx3270, and the feature can be considered deprecated in the other emulators.