dbus call needed to set multiple environment variables in a single pass

Currently, app launching on the Ubuntu phone involves setting multiple environment variables with the SetEnv dbus call. The GetEnv call only takes one variable (key,value) at a time. As a result, the marshalling of the individual calls (and waiting for upstart's response) is reported to have a measurable impact on application startup time.

We should investigate having a dbus call that allows setting multiple environment variables at once, to reduce this overhead.