Version identification now uses both API level and Gerrit build ID

Version number logged at launch and returned from "GET /" now looks like
"SyncGateway/1.00 (1337; commit 1deadb0f)"
The first version number is the API level which is interpreted by CBL.
The second number is Gerrit's build number.
The third is the Git commit SHA.
Logging defaults to non-color (i.e. without ANSI escape sequences)

To enable color, use -log=color flag