JS: read input files on the Swing thread
JS: read input files on the Swing thread

Avoids synchronization conflicts with the updateUI methods.

Signed-off-by: Harry King <409587b9e6671aa0763646191d292852dc49a658@gmail.com>

jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim