Makes the enum strongly typed. A function for retrieving the string
representation of the enum is also added, which allows hiding the array
that contains all of the strings from view (i.e. we operate on the API,
not the exposed internals). This also allows us to bounds check any
querying for the strings.

Avoids potentially using the values uninitialized. While we're at it,
also drop the prefixed underscores from one of the constructors.

And related ARCodeAddEdit/PatchAddEdit.

Change ISOFile to use wxImage instead of wxBitmap since bitmaps require
a screen context and banner images have a fixed resolution.

CreateCodeTab, ARCodeAddEdit and PatchAddEdit
need to be able to modify arCodes/onFrame.

Make iso properties non modal.