elementary: Support using no frame object
Creation of the frame object can lead to significant delays in window
creation time on limited-power devices (watches, mobile, tv, etc).
This patch allows setting an environment variable and config value in
order to completely skip frame object creation.
This shaves about 50ms from startup on an i7 8600k, so should be more
substantial a saves on limited-power devices.
Reviewers: kimcinoo, ManMower
Reviewed By: ManMower
Differential Revision: https://phab.enlightenment.org/D7305