Above staff / below staff placement.

Extends supports for element placement above / below staff:

*) ElementLayout
*) BSymbol, FSymbol, Symbol
*) Text, SimpleText, TextStyle, TextStyleData (with derived classes & relevant dlg boxes)
*) inspector
*) updated definitions of built-in default styles
Fix bug detected by dynamic test suite
Fix textstyle-ref.mscx file in compat test suite to new text style settings
Fix tests to suit changes in tag sequence