Update Jenkins Importer to support XML 1.1

Problem Definition

Since Jenkins version 2.105, the config.xml files in the JENKINS_HOME that store Job definition are defined as XML v1.1 and not 1.0.
The Bamboo Jenkins Importer only supports XML 1.0.

Suggested Solution

Upgrade the importer to support XML 1.1

Why this is important

This will help new Bamboo users coming from Jenkins.

Workaround

You may be able to update the XML version in your config.xml files, but please try this in a test or clone of the instance so you don't affect the running Jenkins instance.