Temporarily locking redraws during complex updates

The updating of tables and graphs during processing of data in a run can be temporarily disabled using the "Lock Drawing" system attribute. When set non zero this prevents the screen being updated. The modeller should force a full repaint after setting this attribute back to 0.

This enables a model to perform complex updates without the intermediate results being redrawn.

The platform always resets the lock when going to "paused" (ready) state and automatically forces a repaint.

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idkbase note 108