Make the icons configurable

[w2w-minjer]

Hi,

i wanted to display another icon for our control but noticed that the icon isn't configurable. I'v seen the issues #36 #56 and both are resolved by removing the dependency.

However, i want to use another icon, one that sits in the material icons which i have as an dependency.

I tried to fix this by making the icons configurable. See pull request: #135