Improvement of SmNodeToTextVisitor

Background: When editing is carried out visually the node tree that represents a formula in memory is modified directly, the SmNodeToTextVisitor generates the command text for the formula, which is used to update the command text box in the bottom of the window. Without this visitor combination of visual and old-school command editing wouldn't be possible. The current implementation of SmNodeToTextVisitor inserts a lot of unnecessary brackets in the generated command text, to ensure that the structure is correct. Removing too many of them would create problems, and there are obscure cases where some extra brackets are needed and cases where no brackets are needed at all. Any improvement of this visitor would be very welcome. Note: The best format documentation is parser.cxx and nodes documentation is in nodes.hxx, but this task is probably easier to solve through trial and error.

Some specific things:

    Reduce the amount of whitespace, find some reasonable policy for whitespace usage.
    Use ^, _, from and to instead of rsup, rsub, csub and csup, depending on context (See this post). 

Skills: Building, C++