Partial port of GTExtensions for P9+, removed configuration

[JanBliznicenko]

• Partially recreated inspector views from GTExtensions. They lack much of the original functionality, syntax highlighting etc., but it's a start.
• Baseline loads these new inspector extensions in Pharo 9+ and loads old GTExtensions in Pharo 6-8.
• Removed direct dependency on XMLWriter (as it is loaded through XMLParser)
• Removed Configuration.

[JanBliznicenko]

Before this is merged, the XMLParser dependency needs to be updated to version that would use my new changes. For that, new release of XMLWriter is needed, then XMLParser needs to point to it, then XMLParser release is needed, then this PR can be finished and merged.