ENYO-2727: refactoring of the kinds related to the definition of an icon/splash screen row.

Now, there is two kinds used to define icon/splash screen row in the panel Phonegap build :
* The Android img row
* the generic img row that can be applyed to all other platforms
This generic img row let the user define the icon's path, the icon's width and height.
These attributs are also added in the config.xml file