used EvalString @ homalgSendBlocking @ String for external GAP elements

+ installed homalgSetName for external GAP elements
added attrib(B,\"isSB\",1); to DecideZeroRows and DecideZeroRowsEffectively

+ second argument of DecideZeroRows and DecideZeroRowsEffectively is (casted to) a module
+ DecideZeroColumns now used DecideZeroRows

this avoids Singular's warning (stdout): // ** _ is no standard basis