imporvements to uninitializedFill && initializeAll

Because they didn't really handle all of the cases correctly.

Added unittests.
"Ranges..." => "Needles..." in [starts|ends]With.
To avoid any confusion: The stuff in ranges may or may not actually be ranges. generic "Needles" is what best describes it.
Clean up endsWith unittests
Original author wrote "wrap" because filter is not bidirectional. However, the function filterBidirectional fits the need, so migrating to that.
Bit of unicode unittest in [starts|ends]With
Just sprinkling some tests. These covered a wee little bit of missing usecases.
Optimizations in startsWith
* Consolidate implementation by checking length in a single spot.
* Checks narrow string or the same types' lengths.
* Index iterates on all RA ranges (and not just Arrays).

Ends with was left untouched, because it forwards to startsWith anyways.
Optimization in startsWith(Range, Needles...)
Basically, makes it stop searching as soon as an element as matched.

This is an important optimization, that avoids a lot of startsWith's other "non-optimzations"...
Implement nextPermutation for bidirectional ranges.
Implement nextEvenPermutation.
Improve ddocs for nextPermutation and nextEvenPermutation.
Improve documentation.
Add unittests for non-default sorting order.
Fix rollover bug in nextEvenPermutation.
Add non-trivial example for nextEvenPermutation.
Oops, fix typo in ddoc.
Issue 8367 - Insufficient constraints for chain

The error message from compiling the bug's sample code after this change is:

```
bug.d(11): Error: template std.range.chain does not match any function template declaration. Candidates are:
std/range.d(2018):        std.range.chain(Ranges...)(Ranges rs) if (Ranges.length > 0 && allSatisfy!(isInputRange, staticMap!(Unqual, Ranges)) && !is(CommonType!(staticMap!(ElementType, staticMap!(Unqual, Ranges))) == void))
bug.d(11): Error: template std.range.chain(Ranges...)(Ranges rs) if (Ranges.length > 0 && allSatisfy!(isInputRange, staticMap!(Unqual, Ranges)) && !is(CommonType!(staticMap!(ElementType, staticMap!(Unqual, Ranges))) == void)) cannot deduce template function from argument types !()(MapResult!(__lambda2, Foo[]),string)
```

Fixes Issue 8367
http://d.puremagic.com/issues/show_bug.cgi?id=8367
Fix 8368 - Insufficient constraints for sort

Error from bug code after this change:

```
Error: template std.algorithm.sort does not match any function template declaration. Candidates are:
std/algorithm.d(7820):        std.algorithm.sort(alias less = "a < b", SwapStrategy ss = SwapStrategy.unstable, Range)(Range r) if ((ss == SwapStrategy.unstable && (hasSwappableElements!(Range) || hasAssignableElements!(Range)) || ss != SwapStrategy.unstable && hasAssignableElements!(Range)) && isRandomAccessRange!(Range) && hasSlicing!(Range) && hasLength!(Range))
bug.d(6): Error: template std.algorithm.sort(alias less = "a < b", SwapStrategy ss = SwapStrategy.unstable, Range)(Range r) if ((ss == SwapStrategy.unstable && (hasSwappableElements!(Range) || hasAssignableElements!(Range)) || ss != SwapStrategy.unstable && hasAssignableElements!(Range)) && isRandomAccessRange!(Range) && hasSlicing!(Range) && hasLength!(Range)) cannot deduce template function from argument types !()(MapResult!(__lambda2, string[]))
```

Fixes Issue 8368
http://d.puremagic.com/issues/show_bug.cgi?id=8368
Update for documentation as a consequence for https://github.com/D-Programming-Language/phobos/pull/862
support for non RA with length in startWith

As suggested by Andrei.

Also: More unittests
Issue 6066 - std.container: BinaryHeap interface is broken.
Issue 5726 - boyerMooreFinder hangs when finding