Icon, REDUCE Configuration, Split Pane and Typesetting Updates

• Introduce a new icon based on a double-struck (i.e. blackboard bold) capital R and also use it in the About alert.
• Switch building to Java 14, set to language level 11, and JavaFX 15.
• REDUCE Configuration dialogue:
  • Ensure that command labels are unique.
  • Make the Check Command check box visible only if the Use Shell check box is selected, which it is by default.
  • Make the REDUCE Packages, Manual and Primers Directory fields directory chooser initial directory the value of the REDUCE Root Directory field if it is set, otherwise its platform default value. This is useful for a non-standard Windows snapshot installation or a Subversion build.
• Split Pane mode:
  • You can now select the other REDUCE panel by pressing Control+Tab, Control+PageDown, Control+Shift+Tab, or Control+PageUp, which matches the default keyboard shortcuts for a TabPane.
  • First implementation of synchronised scrolling of REDUCEPanels, which is relative to the maximum scroll distance, i.e. the content height minus the window height.
• The script files now run Run-REDUCE asynchronously, allow spaces in the JAR file path, and avoid a console window on MS Windows; see the Install and Run Guide.
• Port typesetting support from tmprint for atan2(y,x), m_Gamma(a,z), Lambert_W(x); BernoulliP(n,x), EulerP(n,x), FibonacciP(n,x); Bernoulli(n), Euler(n), Fibonacci(n), Stirling1(n, m), Stirling2(n, m), Motzkin(n).