Expand data loader support

[zgornel]

Some out of the box data loaders should be available:

• databases (ODBC?)
• knowledge graphs (the most known)
• streaming data (i.e. request-index-request looping on some pattern?)

[jpsamaroo]

OpenStreetMap data loading support would be interesting as well, allowing users to query for data within a geospatial area, or along a route (like how Google Maps can show gas stations, coffeeshops, etc. along a route).

[zgornel]

I know ^_^ ! Even better, embedding that stuff. Its in the plan :) but have a bit of a busy period now. We can brainstorm this stuff, I believe that some graph-based embedding approach for openstreetmap can work and would be quite fast. I don't know how it would be handled by julia-db but I suppose it should not be a problem for small maps. For larger ones, probably more engine instances are required and some context broker to route requests...