[doxygen] Component::extendFinalizeFromProperties()
[doxygen] Component::extendFinalizeFromProperties()

Fixed old documentation (LAST -> first) and a typo.

I also mentioned that the System is not available yet in extendFinalizeFromProperties().
opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core