hVision help pages

The hVision help system uses simple HTML pages. Press F1 in any graphical window to open the help page in the current directory, or in a "help" directory under or above the current one, with the same name as the program executable and extension ".html". If this page does not exist, we try the window name, or finally a default "help.html".

We can write the help files using markdown, LaTeX (Mathjax), and syntax highlighting of code samples (hscolour).