Fuel build cache handling

- Cache invalidation supported in case cache is outdated compared to upstream.
- Fully automated build.sh integration tests added (build.sh -t or build.sh -T)
- Rebased to Daniel Smiths's patch-set: genesis refs/changes/71/171/4
- Yet untested, will perform automated integration tests over night!
- Updated based on Stefan's comments (no more revs.)
- Fixed a bug in f_odl_docker/Makefile
- validate-cache target added in f_odl_docker/Makefile

JIRA: BGS-1

Change-Id: I9f8f30c2a85fd7bf04dab1b566065e5739d4fcb1
Signed-off-by: Jonas Bjurel <jonas.bjurel@ericsson.com>