Expose size settings in IconicsImageDrawable
It is quite common to have an `ImageView` with a size of e.g. 40dp but containing a centered 24dp icon, to increase the touch-responsive area. Currently, using an `IconicsImageView` causes the icon to expand to fill the whole space. Exposing `IconicsDrawable.setSizeDp()` etc. as parameters of `IconicsImaveView` would resolve this.
