History of Indexed collections

Fixed a spelling mistake of reduceRight() method

Because it the Array.filter method (as is written in the method's intro) returns an array and not a string.

Because it the Array.map method (as is written in the method's intro) returns an array and not a string.

Fixed per bug 1286078

Corrected spelling mistake.

Remove description about Array generics

moved array comprehension section to array comprehension page