Removed debug baud rate setting

The DEBUG_BEGIN() macro must be called from the main program. No errors
will be reported if it is not called, but debug messages will not be
printed.
Larger input buffer and block on connection

The input buffer is now 128 characters and there is no attempt to
handle longer messages. An input flush() function would be useful.

Writes now block until a connection is established. Not only does
this help with the reliabilty of the data connection, but it prevents
data writes from interfering with command (AT) messages.
Changed state pin variable naming
Test program now demonstrates baud changes

BT connection must be re-established after each rate change.
Tweaked command mode enter/exit delays
Single buffer for inputs, handle multi-line input
Reduced buffer size - possible side effects!!

See the ATTENTION comment in HC05.cpp describing the issue
with timeout vs termination character in the readBytesUntil()
function.
Test for multi-line response

Aside from the readBytesUntil() timeout/termination problem, sending
repeated commands to the HC-05 is not 100% reliable. The problem is
worse when 'connected', but can still be observed when disconnected.
The command appears to not be recognized because there is no response-
not an OK nor an error.