Start work on adding unit tests to our cli code in order to have to
write less costly integration test.
Signed-off-by: Vincent Demeester <vincent@sbr.pm>
In the API:
`Writable` changed to `ReadOnly`
`Populate` changed to `NoCopy`
Corresponding CLI options updated to:
`volume-writable` changed to `volume-readonly`
`volume-populate` changed to `volume-nocopy`
Signed-off-by: Brian Goff <cpuguy83@gmail.com>