* add cache, update cache w/piece create/delete
* add service w/loop to cache to recalculate space used cache
* add piecestore cache to other sn svcs to use
* add table to persist the total space used
* rm cache where not needed
* rm stuff from sn svcs
* start fixing tests, changes per comments
* update commits
* add unit tests
* fix commiting before we write header bytes
* fix cache create test
* copy cache map, add started back to recalc
* fix test
* add test, update comments
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