e/cserve2: add restart code for cserve2
e/cserve2: add restart code for cserve2

Summary: If cserve2 crashes, enlightenment_start will respawn it again.

Test Plan:
Start E18 (in Xephyr maybe) with E_CSERVE set.
Randomly kill evas_cserve2 and enlightenment, and log out from E.

I need review for this patch as I'm not sure about all the ptrace stuff
lying around.

Reviewers: cedric

CC: raster, zmike

Differential Revision: https://phab.enlightenment.org/D287

Signed-off-by: Cedric Bail <187f5756c6b4c71be320f6aaed39b7eac22eddbc@samsung.com>

rvandegrift/e,tizenorg/platform.upstream.enlightenment,rvandegrift/e,rvandegrift/e,tasn/enlightenment,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,FlorentRevest/Enlightenment,tasn/enlightenment