Support custom ImageView

[EricLVertiGIS]

Description

SfButton has the property ImageSource, which is then used to render the Image. The property for the image is ActualImage in ButtonBase.cs. Instead of specifying the source, I would like to be able to assign the ActualImage property directly in order to put our custom, child class of Image into ActualImage.

Additionally, are we able to specify the spacing between the text and the image ? Could we specify the max lines for the text ?

Public API Changes

Make ActualImage property public or protected. Or expose a property for users to configure the Image view in SfButton.

Intended Use-Case

For us, we created a child class of Image that has the ability to tint images. We would like to place the tinted image into the SfButton. But the current SfButton only allows us to specify a source.