SS-3009 Use account ID with token authenticator.
SS-3009 Use account ID with token authenticator.

The token authenticator doesn't send the X-Account header. This is
required for the CM16 API. So added a NewTokenAuthenticatorWithAccountID
function which will set the account ID and use it in the X-Account
header upon signing the request if provided.

rightscale/rsc,rgeyer/rsc,rightscale/rsc,rgeyer/rsc,rightscale/rsc,rightscale/rsc,rgeyer/rsc,rightscale/rsc,rgeyer/rsc,rgeyer/rsc