Adds support for unqualified namespaced XML content (#1590)

Adds support for unqualified namespaced XML content and fixes how qualified namespace URIs values are retrieved.

Fixes gh-1571

docs/src/main/asciidoc/_project-features-contract.adoc

@@ -1843,6 +1843,54 @@ public void validate_xmlMatches() throws Exception {
 ----
 ====
 
+==== XML Support for Namespaces
+Namespaced XML is supported. However, any XPath expresssions used to select namespaced content must be updated.
+
+Consider the following explicitly namespaced XML document:
+
+[source,xml,indent=0]
+----
+<ns1:customer xmlns:ns1="http://demo.com/customer">
+    <email>customer@test.com</email>
+</ns1:customer>
+----
+The XPath expression to select the email address is: `/ns1:customer/email/text()`.
+
+WARNING: Beware as the unqualified expression (`/customer/email/text()`) results in `""`.
+
+For content that uses an unqualified namespace, the expression is more verbose. Consider the following XML document that
+uses an unqualified namespace:
+
+[source,xml,indent=0]
+----
+<customer xmlns="http://demo.com/customer">
+    <email>customer@test.com</email>
+</customer>
+----
+The XPath expression to select the email address is
+```
+*/[local-name()='customer' and namespace-uri()='http://demo.com/customer']/*[local-name()='email']/text()
+```
+WARNING: Beware, as the unqualified expressions (`/customer/email/text()` or `*/[local-name()='customer' and namespace-uri()='http://demo.com/customer']/email/text()`)
+result in `""`. Even the child elements have to be referenced with the `local-name` syntax.
+
+====== General Namespaced Node Expression Syntax
+- Node using qualified namespace:
+```
+/<node-name>
+```
+- Node using and defining an unqualified namespace:
+```
+/*[local-name=()='<node-name>' and namespace-uri=()='<namespace-uri>']
+```
+NOTE: In some cases, you can omit the `namespace_uri` portion, but doing so may lead to ambiguity.
+
+- Node using an unqualified namespace (one of its ancestor's defines the xmlns attribute):
+```
+/*[local-name=()='<node-name>']
+```
+
+
 [[contract-dsl-multiple]]
 === Multiple Contracts in One File