Add documentation on themes, move some themes around

Docs/Themes/observation_towers.md

@@ -0,0 +1,39 @@
+
+
+ Observation towers ( observation_towers) 
+------------------------------------------
+
+
+
+Publicly accessible towers to enjoy the view
+
+This theme contains the following layers:
+
+
+
+  - [observation_tower](../Layers/observation_tower.md)
+  - [gps_location](../Layers/gps_location.md)
+  - [gps_location_history](../Layers/gps_location_history.md)
+  - [home_location](../Layers/home_location.md)
+  - [gps_track](../Layers/gps_track.md)
+
+
+Available languages:
+
+
+
+  - en
+  - nl
+  - de
+  - it
+  - ru
+  - zh_Hant
+  - hu
+  - ca
+  - es
+  - fr
+  - nb_NO
+  - da
+ 
+
+This document is autogenerated from [assets/themes/observation_towers/observation_towers.json](https://github.com/pietervdvn/MapComplete/blob/develop/assets/themes/observation_towers/observation_towers.json)