streams for copying

Implements read/write streams for copying. This is unfortunately a bit more complex than needs to be for good performance as the node stream API assumes ordered data and thus makes concurrent get/put tile handling up to the implementer to do behind the scenes.

Not ready yet.

- [x] update copy command, add tests copy command
- [x] branch of tm2 for some real live testing of performance
- [x] more tests for mem usage/concurrency esp of pyramid stream
- [x] concurrency as option