Move single-element predicate-only find above subrange find
Properly document BoyerMooreFinder

Before it was ditto-ing the find(haystack, needles) docs which return a
tuple instead.
Move boyerMooreFinder above the struct so ddoc finds a parameter name.
Remove note about bug 4759, which is now resolved.
Remove broken glossary links
Merge pull request #2779 from ntrel/find-docs

Improve std.algorithm.find overload docs
List walkLength under convenience functions rather than capabilities
Merge pull request #2781 from ntrel/range-walklength-ref

std.range.primitives: List walkLength under convenience functions rather than capabilities