Add small fixes, additions, comments to interactive example

Still work in progress
cosmos/manu::get accept 'select' field to limit fields returned

If specified the value of select will be used to filter the
entity properties returned so the client can limit what is
retrieved for performance & other reasons

Specs need to be written testing this feature
Use cosmos/manu field 'selection' in systems_with_most stat

Optimizes stat retrieval in case of many systems / entities.
Change should also be applied to other stats at some point
Add some TODO comments