Add a constructor forToastMessage that takesToastType only.

With the newRenderFragment toast content a constructor that takesToastType but not a string message now makes sense.

At the same time make some changes to other constructors:
o Invoke simpler constructors from more complex ones to avoid duplicating code
o Use default argument forautoHide instead of writing two separate constructors
o AddautoHide parameter to constructor that takesIconName to mirror the constructor that takescustomIconName