Enhance GAP.@wrap and GAP.@gapattribute macros

[fingolfin]

1. For @gapwrap we could teach it to auto-convert arguments to GapObj if necessary. So for example, if we have

   GAP.@wrap IsCyclic(x::GapObj)::Bool

   then the funtion this generates could be made equivalent to the following (ignoring for simplicity of the argument the optimizations performed by GAP.@wrap):

   IsCyclic(x::Any) = GAP.Globals.IsCyclic(GapObj(x))::Bool

   Note that it inserted GapObj(x) instead of x to force the argument to be a GapObj. Of course if the argument type is something different, e.g. ::Any we don't need this. (We can discuss what to do about other types like e.g. GAPInt or GAP.Obj, but these are less common)

2. For @gapattribute we could add a variant of this macro to Oscar which checks for GAPWrap instead of (or in addition to) GAP.Globals, so that we can rewrite

   @gapattribute is_cyclic(G::GAPGroup) = GAP.Globals.IsCyclic(GapObj(G))::Bool

   as something like this (the ::Bool is now redundant as the IsCyclic wrapper already has it)

   @gapattribute is_cyclic(G::GAPGroup) = GAPWrap.IsCyclic(GapObj(G))

   or indeed, when combined with the changes to the @wrap macro, to

   @gapattribute is_cyclic(G::GAPGroup) = GAPWrap.IsCyclic(G)