started AlgebraicThomas wrapper package
QuasiAffineSet( I, J ) sets IsEmpty resp. IsAffine to true

if ( IsOne( I ) or IsZero( J ) ) resp. IsZero( J )

+ take care of empty matrices
declared and installed QuasiAffineSet for one argument
declared and installed ADefiningIdealOfComplement
support field extensions

(needs RingsForHomalg v2013.07.04)
declared and installed Project

we needed to reverse the list of indeterminates passed to the constructor
of quasi-affine sets as Thomas B. follows Daniel's convention which prefers
the last variables, preventing a projection on the base k[x] of k[x][y]

added example