Add function to calculate the median of a set of numbers

[delphidabbler]

There should be different implementations of Median for floating point and integer medians:

function Median(const A: array of Extended): Extended; overload;
begin
  Assert(Length(A) > 0);
  // optimisations for array lengths 1 & 2 to avoid sorting
  if Length(A) = 1 then
    Exit(A[0]);
  if Length(A) = 2 then
    Exit((A[0] + A[1]) / 2.0);
  Generics.Collections.TArray.Sort<Extended>(A); // using standard comparer
  var MiddleLo := Length(A) div 2;
  if Odd(Length(A)) then
    Result := A[MiddleLo + 1]
  else
    Result := (A[MiddleLo] + A[MiddleLo + 1]) / 2.0;
end;

function Median(const A: array of Integer): Extended; overload;
begin
  Assert(Length(A) > 0);
  // optimisations for array lengths 1 & 2 to avoid sorting
  if Length(A) = 1 then
    Exit(A[0]);
  if Length(A) = 2 then
    Exit((A[0] + A[1]) / 2);
  Generics.Collections.TArray.Sort<Integer>(A); // using standard comparer
  var MiddleLo := Length(A) div 2;
  if Odd(Length(A)) then
    Result := A[MiddleLo + 1]
  else
    Result := (A[MiddleLo] + A[MiddleLo + 1]) / 2;
end;

This issue was extracted from issue #16

[delphidabbler]

The implementations proposed in the above comment was incorrect. The versions actually added to the collection are correct.

[delphidabbler]

Implemented by merge commit 0bbdeb5