Layers should not have checkboxes with Mapguide tiled maps

[zspitzer]

Fusion currently displays checkboxes for mapguide layers in a base layer group, these have no effect as you can only toggle the base layer group.

When there is only one base layer group, it can't be toggled either

This is easily reproducible by creating a flexible layout using the sheboygan sample (there are no tiled flexible layout in the sample)

every checkbox in the legend is currently redundant

[madair]

fixed at rev 1926