Add Option to Highlight Changes in Syntax Trees

[daveaglick]

Add the option to highlight changes between the original input query and the syntax tree output in the SyntaxTreePanel text view. This will be valuable when dealing with analyzers and code fixes. Some questions:

• How to correlate non-root nodes with the corresponding position in the original text?
• How to handle syntax trees from external sources (since there's no original text to read from)?

In this end, this idea may not be practical.