python-rpc: add console.py

It allows one to connect to a running daemon or wallet, and use
its RPC API from python.

Usage: python -i console.py <port>

It will detect whether it's talking to a daemon or wallet and
initialize itself accordingly.

tests/functional_tests/functional_tests_rpc.py

@@ -60,7 +60,7 @@ try:
   PYTHONPATH = os.environ['PYTHONPATH'] if 'PYTHONPATH' in os.environ else ''
   if len(PYTHONPATH) > 0:
     PYTHONPATH += ':'
-  PYTHONPATH += '../../utils/python-rpc'
+  PYTHONPATH += srcdir + '/../../utils/python-rpc'
   os.environ['PYTHONPATH'] = PYTHONPATH
   for i in range(len(command_lines)):
     #print('Running: ' + str(command_lines[i]))