creation of a standalone jar using maven-shade-plugin

This enables Maven to control the distribution of all required jars. The
resulting standalone jar has the same usage as the
fitnesse-standalone.jar.

issues left:
- source code of hsac-fitnesse-plugin should be added to the project
- take-snapshot writes files to target in stead of wiki directory
- rename the project to hsac-fitnesse-standalone in stead of
hsac-fitnesse-fixtures