Add generic call to create Ecore_Evas from engine names.

Add generic call to create Ecore_Evas from engine names.

One can get engine names with ecore_evas_engines_get() and present
them to its users (from --help, for example) and then give that name
to ecore_evas_new(), that accepts the name, geometry and extra options
as a string.

As I don't have all the engines here, I might have missed something
from those, tested here:

 - software_x11
 - xrender_x11
 - opengl_x11
 - directfb
 - buffer

git-svn-id: http://svn.enlightenment.org/svn/e/trunk/ecore@35919 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33