Add OpenMapTiles Server to non-free.md

Ref. #1284

Add [OpenMapTiles Server](https://openmaptiles.org/) by [Klokan Technologies](https://www.klokantech.com/).

Reasons for non-free listing: The software is only [available](https://openmaptiles.org/docs/) as docker images, https://hub.docker.com/r/klokantech/openmaptiles-server/~/dockerfile/ is blank, only a binary blob is available  It is partly built on Free software listed at https://github.com/openmaptiles.

+ Fix Elastix entry (Remove link to https://svn.code.sf.net/p/elastix/code/ (unmaintained since 2016), Remove obsolete GPLv2 mention, Remove PHP tag - software is only distributed as an ISO image).

non-free.md

@@ -47,9 +47,13 @@
 
 ## IPBX
 
-  * [Elastix](http://www.elastix.org) `⊘ Proprietary` - Unified communications server software based on 3CX. ([Source Code](https://svn.code.sf.net/p/elastix/code/trunk/)) `GPLv2` `PHP`
+  * [Elastix](http://www.elastix.org) `⊘ Proprietary` - Unified communications server software based on 3CX.
 
 
+## Maps & GPS
+
+  * [OpenMapTiles Server](https://openmaptiles.org/) `⊘ Proprietary` - Set of tools for self-hosting of OpenStreetMap vector tiles. ([Demo](https://openmaptiles.org/), [Partial Source Code](https://github.com/openmaptiles)) `Python/JavaScript`
+
 ## Media Streaming
 
   * [Plex](https://plex.tv/) `⊘ Proprietary` - Plex is a centralized home media playback system with a powerful central server.