Provide manual parameter for 'spotsize' in GAL exporter
Since the 'spotsize' column wasn't added until BASE 2.7 (#999), many existing array designs doesn't have this value, even though it was present in the TAM file they were imported from. Since it is not possible to re-import or change the imported values there is currently no way to export the "correct" spot size in the GAL file. The GAL exporter (#994) needs a parameter asking for a spot size. The parameter should be optional and if left empty the values from the database should be used.