GIS module for Sahana Eden 2.0

Upgrade to new JavaScript libraries

The core JavaScript Mapping Library that we use is still ​OpenLayers 2.x
This is very old and we would benefit from upgrading to the ​current 6.x release

• no need to maintain the old one for browser changes (Just 1 instance of that so far: )
• we can take advantage of new features & performance upgrades (like ​TileJSON)

At the core this isn't too hard and ​much progress has already been made (& UCCE already uses OL5 within the DC Editor) The big issue is the User Interface, especially for the main map. This is currently built on ​GeoExt 1.1 & !ExtJS 3.4. The obvious solution would be to upgrade to the ​current GeoExt, and hence ​ExtJS 6.2, however that version of ExtJS is no longer available and has ​strict GPL licensing around it, which doesn't really make it suitable for us.
GeoExt are also not moving very fast and a dependency on that seems unwise if we're making a big change anyway.
Although we could bring in the GeoExt code that we use and maintain it ourselves (it is BSD-licensed), it depends on !ExtJS, which is not, so this isn't really an option.
So what UI toolkit should we use instead?
An obvious option would be ​jQueryUI, since we already use that extensively for custom widgets in Eden, and we already use the widget factory for our ​OL6-version of the Map
Although it hasn't received many upgrades recently, it is still maintained with a ​new release coming soon. It has limited Widgets available: Buttons, Dialog, Menus, Tabs all there, but no Toolbar (we can probably use Controlgroup for this) Panels or Tree (using ​JSTree seems the right approach here, as we already use this elsewhere & it's well-maintained). We can also see about bringing in components from ​PrimeUI...that isn't maintained, however the Apache 2 license means we can take anything we want from there.

There are other options which we could consider:

• !VueJS
  • Basic Tree example: ​https://v3.vuejs.org/examples/tree-view.html
  • PrimeVue has widgets: ​https://primefaces.org/primevue/
• Angular
  • TypeScript-only :/
• BackBone/Mustache
• BluePrint
  • ​https://blog.palantir.com/scaling-product-design-with-blueprint-25492827bb4a
  • looks good, but Palantir :/ & no Mobile :/ & TS :/
• Ember
• Lit (lightweight web components)
• React
  • ​https://react-md.dev/packages/tree/demos
• ​Webix
  • GPL, but can be combined with MIT
  • Has a Tree

Other Issues

• Import / Export ​SLD <> gis_style
  • Should be pretty easy as our model is basically a JSON version of SLD anyway
• Import / Export ​WMC <> gis_config
• Import for Shapefile needs completing
  • ​https://github.com/sahana/eden/blob/master/modules/s3/codecs/shp.py#L239
• Export to Shapefile should use Python-GDAL bindings not shell utilities
  • ​https://github.com/sahana/eden/blob/master/modules/s3/codecs/shp.py#L179
• Filtered Maps (e.g. Summary/Map methods) trigger 2x requests to the server for the GeoJSON