Escrow mode update

In escrow mode, only raise the escrow event 1 time per escrow sequence

Due to the nature of RS-232 polling, the slave will always report "escrow" immediately after a stack or return command. This
commit adds a filter to guarantee that this escrow state change is handled more like a single shot event instead of a state. Since
the escrow state change is originally reported, this does not necessarily break the state machine. The only instance in which this
change may be problematic is if you are actively switching on the state in client side code. From what I've seen, clients are more
passive about state change so I do not anticipate any issues.

Also included in this release is an optional dll signed with a strong name key.