utils/ssh: Add paramiko based scp transfers

Using scp over paramiko allows scp transfers to be treated similarly to
sftp transfers, instead of requiring subprocesses, and provides
the ability to monitor an scp transfer using a callback as can be done
using sftp.

setup.py

@@ -83,6 +83,7 @@ params = dict(
         'pexpect>=3.3',  # Send/recieve to/from device
         'pyserial',  # Serial port interface
         'paramiko', # SSH connection
+        'scp', # SSH connection file transfers
         'wrapt',  # Basic for construction of decorator functions
         'future', # Python 2-3 compatibility
         'enum34;python_version<"3.4"', # Enums for Python < 3.4