JS: Throw more general error when no key, KeyInput parsing fails
JS: Throw more general error when no key, KeyInput parsing fails

- errors were properly thrown when a non-existent entity was used in
KeyInputs, however, the error message didn't make much sense because
it had been parsed as a value
- this correctly gives an "entity not found" error when a bad key is
used
- correctly gives a "bad value" error when an invalid value is used
- bad second value to inputs gets caught and throws an exception
soon after the new try/catch

Signed-off-by: Eric Finlay <0515159691d711daa95426d2e7114f1a85afa555@ausenco.com>

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