Removed old text buffer/display that was accidentally committed.
Started a global preferences dialog

So far, it only configures the font for the script editor, and the
icon/button is not the final version.
Settings that fail to execute are disabled

Instead of permanently disabling settings, however, they are now only
ephemerally marked as failed. Editing them will re-enable them. (This
workflow will be made more obvious in the future.)

Also, some progress with selections and hyperlinks and a bit of cleanup
in the code.