createChildWithNewPrefix
Creates an AssertionFormatterParameterObject for kind of a child of the current parameter object using the given newPrefix (the child will typically be used to indent Assertions one level more).
Technically speaking it means that the child's indentLevel is based on the current parameter object but increased by the current parameter object's prefix.length.
Return
The newly created AssertionFormatterParameterObject.
Parameters
newPrefix
The new prefix to be used.