XMLUnit for Java 2.8.3

This release fixes a shortcoming of the AssertJ support modules and adds a new convenience feature to the Diff class.

The full list of changes:

• added a new fullDescription method to Diff that provides a string-representation of all differences - not just the first one like toString does.
  PR #235 fixing #232 by @Boiarshinov

• made sure AssertJ's methods to override the assertion message like withFailMessage are honored.
  #225

• adjusted unit tests so they pass when AssertJ 3.19.0 is used.
  PR #212 by mmathesius