Add detection for when a Fontsampler uses indistinguishable fonts (identical PS Family Name, weight and width)

[kontur]

As documented in the FAQ the plugin is unable to tell apart variations of the same PS Family Name if their weight and width is the same, i.e. if

ACME Font Stencil ACME Font Rounded ACME Font Regular

all have a PS Family Name of "ACME Font", the font selection and initially selected font will behave faulty.

There isn't a plugin-side solution to this, but the user could be warned about this issue when adding those types of similar fonts to the admin area.

[kontur]

No longer an issue due to 9e98e78