Provide basic experimental formatter which supports invalid XML

[angelozerr]

This issue is used to initialized the new formatter which uses a new strategy to format XML. Instead of rewriting the XML with proper indentation (which causes problem with invalid XML which looses some content) with one TextEdit, the main idea is to generate several TextEdit whith only spaces and line sperator (remove or add spaces before the start tag / end tag element).

This issue will provide a new format stetting "experimental : true" to use this new formatter.

This issue will provide a basic formatter and all existing settings will not take care of. We will improve it step by step by taking care of existing format settings.