[ffi] Consider a loosely typed Android SDK

[ncalexan]

I was reading the Datomic documentation, and they emphasized that the Datomic API is built on the foundations the JVM provides rather than having, e.g., a ResultSet API. From https://docs.datomic.com/on-prem/architecture.html:

The ability to query and access data locally has a profound effect on the code in a Peer. Query results are directly accessible as simple data structures. There is no need to deal with the command and resultset abstractions common to most traditional database APIs, nor the object-relational mapping layers intended to hide them. A simple group of functions that encapsulates building and executing queries and transactions is sufficient.

Now, Datomic's position here is rather different from Mentat's, but there's something to be said for "just lists" and "just data". Maybe we could explore exposing lists-of-maps (ArrayList of HashMap) in the Android SDK and see how it feels?

@fluffyemily do you have strong feelings about this?