Checkpoint first cut at store; compiles but untested.

git-svn-id: svn://graphite/diminuto/trunk@562 5dfbf39a-1452-0410-8a97-9e58fedde8e3
FIrst cust at store unit test passes.

git-svn-id: svn://graphite/diminuto/trunk@563 5dfbf39a-1452-0410-8a97-9e58fedde8e3
Checkpointing after unit test pass following remove fix.

git-svn-id: svn://graphite/diminuto/trunk@564 5dfbf39a-1452-0410-8a97-9e58fedde8e3
Comments mostly.

git-svn-id: svn://graphite/diminuto/trunk@565 5dfbf39a-1452-0410-8a97-9e58fedde8e3