only numVars should work

[matthias-da]

It is a minor issue and should be only solved if it takes not much time, and mabe it would need major changes since the whole print outputs considering categorical key variables...

If no categorical key variables are present, ideally, the creation of an sdcMicroObj should be possible (now error: provide keyVars)

data("Tarragona")
sdc <- createSdcObj(Tarragona, 
           numVars = c("CURRENT.ASSETS", "SALES", "DEPRECIATION", 
                                 "GROSS.PROFIT", "NET.PROFIT"))