allow child controls to specify their own render delegates to be used

Enyo-DCO-1.1-Signed-Off-By: Cole Davis (cole.davis@lge.com)
Merge pull request #736 from enyojs/BHV-8667-coledavis

Fix for: BHV-8667

Looks good!

Reviewed-by: Aaron Tam (aaron.tam@lge.com)