selects the table number whose results will be returned;
use value "last" to select the last table in the .ext file; or pass an
integer specifying the table number; in case there is exactly
one table in the .ext file, pass the value "single" to bypass parsing
the file to look for sub tables (this might be useful when BAYES analysis
was performed as the only estimation method and there are 10000s of
posterior samples in the file)