- Added PhpParser.cs file in Utils with code used to parse PHP files.

- Added PrepareRename public API method into PhpRefactoring class used to find out what can be renamed on the specified position in code.
- Added ContextInfo class used to remember info about context of variables etc.
- Added ContextType enum specifying type of context.
- Added TextSpan struct used to save span in text files (from line/column to line/column).
- Added ExpressionType enum used to separate different expression types.
- Added ContextVisitor used to distinguish different variable context in AST.
- Added SearchVisitor used to find expression on specified position in AST.
- Added CodeRenamer class used to control renaming and finding of expressions in AST etc.