NewportSMC: Avoid crash upon serial receive error.

(Crash was caused by out-of-range access of the answer string.)

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@13778 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
ASITiger: made hub's SerialResponse property read-only, changed underlying implementation a bit (still only shows response from action on SerialCommand property)

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@13779 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd