DOC - partial rewrite of fused types doc
DOC - partial rewrite of fused types doc

After conversation with Mark F today. Change from pointers to scalars
for clarity.  Add quickstart section.  Explain case where the same fused
type in an argument list must be specialized to same type.

dahebolangkuan/cython,mrGeen/cython,dahebolangkuan/cython,madjar/cython,JelleZijlstra/cython,acrispin/cython,hhsprings/cython,JelleZijlstra/cython,acrispin/cython,encukou/cython,hhsprings/cython,mcanthony/cython,dahebolangkuan/cython,acrispin/cython,rguillebert/CythonCTypesBackend,larsmans/cython,larsmans/cython,madjar/cython,cython/cython,slonik-az/cython,da-woods/cython,fabianrost84/cython,madjar/cython,ChristopherHogan/cython,roxyboy/cython,fabianrost84/cython,cython/cython,hhsprings/cython,da-woods/cython,madjar/cython,fperez/cython,cython/cython,andreasvc/cython,rguillebert/CythonCTypesBackend,hhsprings/cython,ChristopherHogan/cython,mrGeen/cython,fperez/cython,andreasvc/cython,ABcDexter/cython,mcanthony/cython,slonik-az/cython,c-blake/cython,hickford/cython,achernet/cython,da-woods/cython,hhsprings/cython,slonik-az/cython,cython/cython,achernet/cython,fabianrost84/cython,dahebolangkuan/cython,achernet/cython,marscher/cython,hickford/cython,andreasvc/cython,roxyboy/cython,rguillebert/CythonCTypesBackend,encukou/cython,mcanthony/cython,mcanthony/cython,acrispin/cython,encukou/cython,madjar/cython,mrGeen/cython,roxyboy/cython,JelleZijlstra/cython,ABcDexter/cython,andreasvc/cython,mrGeen/cython,fperez/cython,rguillebert/CythonCTypesBackend,hickford/cython,JelleZijlstra/cython,encukou/cython,marscher/cython,c-blake/cython,encukou/cython,larsmans/cython,ABcDexter/cython,fabianrost84/cython,scoder/cython,ABcDexter/cython,andreasvc/cython,mrGeen/cython,achernet/cython,marscher/cython,c-blake/cython,slonik-az/cython,hickford/cython,c-blake/cython,fabianrost84/cython,scoder/cython,JelleZijlstra/cython,marscher/cython,fperez/cython,larsmans/cython,marscher/cython,achernet/cython,acrispin/cython,ChristopherHogan/cython,hickford/cython,fperez/cython,slonik-az/cython,ABcDexter/cython,roxyboy/cython,larsmans/cython,dahebolangkuan/cython,da-woods/cython,mcanthony/cython,scoder/cython,c-blake/cython,roxyboy/cython,scoder/cython