I've made a few updates based on some of the feedback in this thread.

- execute() renamed to query()
- query with input binds directly from connection
- query() returns result for chaining

The design is still early stage.  I've got a growing list of design options which I'll bring into discussion once the interface becomes more stable.

Other updates:

- postgres reference implementation added (synchronous only at moment)
- DUB package now available as dstddb
- DMD "cyclic structs" bug fix may land soon (PR appeared) with design improvements to follow.

erik