Add OpenWISP

As mentioned in #439

README.md

@@ -600,6 +600,7 @@ _See also: [IT Asset Management]([Ralph](#it-asset-management))_
 *Network configuration management tools.*
 
 - [GNS3](https://www.gns3.com/) - Graphical network simulator that provides a variety of virtual appliances - ([Source Code](https://github.com/GNS3/gns3-gui/), [Documentation](https://docs.gns3.com/)) - `GPLv3`
+- [OpenWISP](https://openwisp.org/) - Open Source Network Management System for [OpenWRT](https://openwrt.org/) based routers and access points. ([Demo](https://openwisp.org/demo.html), [Source Code](https://github.com/openwisp))
 - [Oxidized](https://github.com/ytti/oxidized) - A modern take on network device configuration monitoring with web interface and GIT storage.
 - [phpIPAM](http://phpipam.net/) - Open source IP address management with [PowerDNS](https://www.powerdns.com/) integration.
 - [RANCID](http://www.shrubbery.net/rancid/) - Monitors network device's configuration and maintain history of changes.
@@ -607,6 +608,7 @@ _See also: [IT Asset Management]([Ralph](#it-asset-management))_
 - [trigger](https://github.com/trigger/trigger) - Robust network automation toolkit written in Python.
 
 
+
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