Added ability to define custome list template

[DavsX]

Added the ability to specify custome template for the list like this:

schema: {
   myList  : {
        type: 'List',
        template: _.template("<div data-items></div>"),
   },
}

This way the Add button can be specified.

[DavsX]

My apologies, apparently I removed the trailing whitespaces too (which is not a bad thing imho)