More review feedback!

ExecutionContexts create their own loggers.

Creator sets the `askari.name` coprocessor argument to the name
appearing on that coprocessor in the schema.  This way a coprocessor
can discover its own definition.

Applications are aware of dispatch rules even if handlers are missing.
The early return in dispatch has also been dropped.  This allows
folding events to return the correct argument instead of nil when no
handlers are present.

Applications can `#serve` each other and exploit modules.

`HRegionAsHTable` is a `HTableInterface` adapter for `HRegion`s.

Really, we'd like a simpler interface than `HTableInterface` to aim
for, but this appears to be the best uniform client interface
available.  It seems most of the methods will simply be ignored.

With this adapter, we should be able to use `HRegion`s from within
`Relation`s (see `ExecutionContext#local_relation`), which is really
all we want.