emotion/aspect: Add API to configure the aspect ratio policy.

emotion/aspect: Add API to configure the aspect ratio policy.

The new function emotion_object_keep_aspect_set() allow to set a policy
that will automatically change the emotion object border property, based
on the video aspect ratio and object current aspect ratio.

Possible values are:
 * EMOTION_ASPECT_KEEP_NONE
 * EMOTION_ASPECT_KEEP_WIDTH
 * EMOTION_ASPECT_KEEP_HEIGHT
 * EMOTION_ASPECT_KEEP_BOTH
 * EMOTION_ASPECT_CROP
 * EMOTION_ASPECT_CUSTOM

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/emotion@63416 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33