Creates a dialog which prompts the user with text to input a text string. The contents of the entry
are put in the variable upon closure of the
dialog. The command returns a boolean indicating if the user
pressed OK or not. If -geometry is not specified, the dialog is
centered in its parent toplevel unless its parent is . in which
case the dialog is centered in the screen. Options: -title
-allowempty a boolean argument indicating if the dialog should
accept an empty entry -entryoptions simply passes its arguments
through to the entry widget. This is valuble for performing extra
validation using the Entry widget validation hooks. -geometry
specifies the geometry of the window