#113 Modal windows

[Mike]

WOuld be great if we had the option (at least) to make
help and other popup windows 'modal'.

Many reasons for this but there is a defect in that if
you leave a help window open while selecting another
help option from the main webmin screen, the help
window contents change but the help window itself does
not regain focus.

Also, it should be mandatory to close a popup
selection box before moving on to do something else in
the main window.

Possible solution is to ensure help windows always
gain focus on selection and to make popup selection
boxes modal.