Add sandbox update/sync instructions
Add sandbox update/sync instructions

Change-Id: I15a1ab126f74a54703dfe6fce54f8d07d237e5cf
Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

twoerner/angstrom-manifest,koenkooi/angstrom-manifest,Angstrom-distribution/angstrom-manifest,linaro-home/lhg-oe-manifests,ndechesne/qcom-oe-manifest,96boards/oe-rpb-manifest