ENYO-3732: use a 'add' Object sepcifying if the properties should be added if absent or just make the substitution in JSON substitution function

Enyo-DCO-1.1-Signed-off-by Junil Kim <logyourself@gmail.com>
ENYO-3732: add condition to check if add variable is undefined

Enyo-DCO-1.1-Signed-off-by Junil Kim <logyourself@gmail.com>
Revert "ENYO-3732: add condition to check if add variable is undefined"

This reverts commit 5eef8173e385f06bdfe87254012d7f4c9517955d.
ENYO-3732: add condition to check if add variable is undefined.

Enyo-DCO-1.1-Signed-off-by Junil Kim <logyourself@gmail.com>
Merge pull request #14 from enyojs/ENYO-3732

ENYO-3732: use a 'add' Object sepcifing if the properties should be added if absent or just make the substitution in JSON substitution function