Specify layer name in add_table_layer

[joaq-ram]

Include ability to specify a data layer name in the add_table_layer() method via a "name = " parameter at the declaration of the layer. This feature exists in the add_image_layer() but has not been implemented with table layers.

[pkgw]

OK, looking into this, the CreateTableLayerMessage used by pywwt does not have a name field yet, so we'll need to add some support for this on the engine side first. This should be simple and analogous to the CreateImageSetLayerMessage, which does have this field.