[mapguide-internals] RFC 77 - Create Feature Source is updated.

[Leaf Li]

All,

I updated MapGuide RFC 77 because of the following reason. Can you review it?

Previously, MgFeatureService::CreateFeatureSource(...) will throw an MgInvalidArgumentException no feature classes or spatial context are specified in the MgFileFeatureSourceParams instance. If the spatial context and feature class are not known at the time of creation then a "dummy" feature class and spatial context would need to be specified; and then deleted later. 

This change will allow MgFeatureService::CreateFeatureSource(...) to execute without the spatial context and feature class specified. 
http://trac.osgeo.org/mapguide/wiki/MapGuideRfc77

Thanks,
Leaf Li