Change definitions of various categories

... to correctly model their meaning, instead of (ab)using InstallTrueMethod
to do so.

Motivated by gap-system/gap#3006

gap/specht.gd

@@ -46,20 +46,23 @@ DeclareCategory("IsHeckeModule", IsAlgebraObjModule);
 DeclareCategory("IsHeckeSpecht", IsHeckeModule);
 DeclareCategory("IsHeckePIM", IsHeckeModule);
 DeclareCategory("IsHeckeSimple", IsHeckeModule);
+
 DeclareCategory("IsFockModule", IsHeckeModule);
-DeclareCategory("IsFockSpecht", IsHeckeSpecht);
-DeclareCategory("IsFockPIM", IsHeckePIM);
-DeclareCategory("IsFockSimple", IsHeckeSimple);
+DeclareSynonym("IsFockSpecht", IsHeckeSpecht and IsFockModule);
+DeclareSynonym("IsFockPIM", IsHeckePIM and IsFockModule);
+DeclareSynonym("IsFockSimple", IsHeckeSimple and IsFockModule);
 ##
 DeclareCategory("IsSchurModule", IsHeckeModule);
-DeclareCategory("IsSchurWeyl", IsHeckeSpecht);
-DeclareCategory("IsSchurPIM", IsHeckePIM);
-DeclareCategory("IsSchurSimple", IsHeckeSimple);
-DeclareCategory("IsFockSchurModule", IsFockModule);
-DeclareCategory("IsFockSchurWeyl", IsFockSpecht);
-DeclareCategory("IsFockSchurPIM", IsFockPIM);
-DeclareCategory("IsFockSchurSimple", IsFockSimple);
+DeclareCategory("IsSchurWeyl", IsHeckeSpecht and IsSchurModule);
+DeclareSynonym("IsSchurPIM", IsHeckePIM and IsSchurModule);
+DeclareSynonym("IsSchurSimple", IsHeckeSimple and IsSchurModule);
+
+DeclareSynonym("IsFockSchurModule", IsFockModule and IsSchurModule);
+DeclareSynonym("IsFockSchurWeyl", IsFockSpecht and IsSchurWeyl);
+DeclareSynonym("IsFockSchurPIM", IsFockPIM and IsSchurPIM);
+DeclareSynonym("IsFockSchurSimple", IsFockSimple and IsSchurSimple);
 
+##
 BindGlobal("HeckeSpechtType", NewType(AlgebraObjFamily, IsHeckeSpecht));
 BindGlobal("HeckePIMType", NewType(AlgebraObjFamily, IsHeckePIM));
 BindGlobal("HeckeSimpleType", NewType(AlgebraObjFamily, IsHeckeSimple));

gap/specht.gi

@@ -1475,19 +1475,6 @@ InstallMethod(Module,"create new module",[IsAlgebraObj,IsString,IsList,IsList],
     return module;
   end
 );
-InstallTrueMethod(IsFockModule,IsFockSpecht);
-InstallTrueMethod(IsFockModule,IsFockPIM);
-InstallTrueMethod(IsFockModule,IsFockSimple);
-InstallTrueMethod(IsSchurModule,IsSchurWeyl);
-InstallTrueMethod(IsSchurModule,IsSchurPIM);
-InstallTrueMethod(IsSchurModule,IsSchurSimple);
-InstallTrueMethod(IsFockSchurModule,IsFockSchurWeyl);
-InstallTrueMethod(IsFockSchurModule,IsFockSchurPIM);
-InstallTrueMethod(IsFockSchurModule,IsFockSchurSimple);
-InstallTrueMethod(IsSchurModule,IsFockSchurModule);
-InstallTrueMethod(IsSchurWeyl,IsFockSchurWeyl);
-InstallTrueMethod(IsSchurPIM,IsFockSchurPIM);
-InstallTrueMethod(IsSchurSimple,IsFockSchurSimple);
 
 InstallMethod(Module,"create new module",[IsAlgebraObj,IsString,IsInt,IsList],
   function(H,m,c,p)