Introduce block_store factory

To allow for reuse of code concerned with constructing different
block_store stacks, a factory directory is added for different
factories to live. Two factories have been added so far: the
ref_ram factory constructs a ram-backed block store, partitioned
using the reference partition configuration expected by test cases.
The client factory constructs a block_storage_client that talks to
a remote block storage service provider.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: Ib4c02f12a0742fc9b75143de612dd273f2bfffa9
13 files changed