Multiple allowed ip/subnet support

This version addresses this issue: #8. In particular:

• Corrected a typo in the label. It was inteface instead of interface.
• Implemented support for multiple allowed ip and subnets. Two label mode are available: single, comma separated value (default) and multiple labels with an incremental number appended. The second mode can be enabled using the -s command line switch.

Thank you Toon Schoenmakers for the idea.