Disabled context menu in chart's web view
Added (very) basic Yelp documentation. Testing needed!
Added Yelp related stuff to .gitignore
Added more help pages.
Updated Hungarian Help translation
Updated .gitignore to protect legal.xml help file
Added Help on pressing F1

This still has many things to do. The help files must be improved,
and the help function must be made context-aware (the current show_help()
function is already context-aware).