Break up the content store prototype into a few logical files. We have a
file for the store, the writer and helpers.
Also, the writer has been modified to remove write and exec permissions
on blobs in the store.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
After experimenting with pull, we've defined a transactional content
store for verified storage of fetched items. A base component of
containerkit, this will interact with both the runtime and distribution
sides of the system, avoiding coupling.
Blob access if provided through direct access to readonly files.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
