This fragment defines the 2 rap extension (for entryPoint and branding)
so as to use the rcp application with single sourcing. Only optional
dependencies to rap.ui have been added in rcp host plugin. 
This fragment is interesting when you want to reuse the workbench of the
rcp application. In case of another workbench (specific for your rap
application), you just extends the entryPoint and branding directly in
the xxx.rap plugin, containing the new workbench.