bulk equivalent of initctl set-env

One of the items that comes up in performance analysis of application startup on the phone is that we spend a fair bit of time doing (IIRC) 16 initctl set-env calls, many of which are required for confinement purposes so I gather we can't easily trim that list. Each call involves a fork, an exec, and a D-Bus method call; in aggregate this is slow, and we should speed it up.

I would suggest that we need:

 (1) an equivalent of "initctl set-env" that can take multiple VARIABLE=VALUE pairs (I don't feel strongly about whether this should be a new command or an extension to the existing set-env command, although the command's existing syntax seems to allow for this extension);
 (2) a new D-Bus method, similar to com.ubuntu.Upstart0_6.SetEnv except that var becomes an array. SetEnv would need to be retained for compatibility.

For orthogonality, the same probably ought to be done for "initctl unset-env".