Scope: Release of v0.9.1

Bug fixes and minor feature additions including final refactor of servlet implementation,
and addition of a proof of concept JSP implementation for future development. Includes
autoomatic "busy cursor" in Swing implementation.

Note that I can get the JSP implementation to run in Tomcat 3.2.3 but not Tomcat 4.0.1.
Needs investigation!

* Fixes and (final?) refactor of servlet implementation.
* Added basic JSP implementation including the start of a custom taglib.
* Added "Introduction to Scope" presentation to docs (Julia Reynolds).
* Added automatic initialisation of XSL SystemID (Beat Glattfelder).
* Added example for servlet requiring user login.
* Added credits page to project web site.
* Unit tests for STable and resulting bug fixes.
* Allowed explicit set of StringConvertor on STextField and SComboBox.
* Added simple automatic "busy cursor" handling.
* Changed semantics of accessing non-existent properties: get now returns
null if traversal through null properties, set throws UnsupportedOperationException.
The View implementation should handle that correctly. To test whether a property
exists before doing a get or set use PropertyManager.hasProperty().
* Added active BasicModel wrapper for java.util.Set: SetModel.