RANDSUBSET  Return random subset of list categories

     [OUT,REST,IND,IND2]=RANDSUBSET(LL,numpar)

 INPUTS
   LL     - sdlist object
   NUMPAR - number of categories or fraction (0,1)

 OUTPUT
    SUB       Selected subset
    REST      Remainder of the list LL
    IND1,IND2 Indices of the samples in SUB and REST

 DESCRIPTION
 RANDSUBSET on SDLIST object can be used to randomly select a subset of categories.