Expands the "fixed size array" section
Expands the "fixed size array" section

Indexing it also as shaped arrays, expanding a bit the examples, and
adding the changes in 2018.09. Closes #2326

MasterDuke17/doc,perl6/doc,MasterDuke17/doc,stmuk/doc,stmuk/doc,perl6/doc,perl6/doc,MasterDuke17/doc,perl6/doc,tbrowder/doc,stmuk/doc,tbrowder/doc,stmuk/doc,tbrowder/doc,stmuk/doc,perl6/doc,MasterDuke17/doc,tbrowder/doc