Add new cluster spec for sync-gateway
Add new installation configuration.
Adding installation for sync_gateway and gateload.
Add logic to create config files for sync_gateway and invoke sync_gateway remotely
Add gateload_tests.py to run it as a test case
Addding sync-gateway to perfrunner

Change-Id: I7cd08b8500367908cbd029a56c29bef95c983a67
Merge branch 'lichenyang2-master'