Group template/function overloads to avoid visual clutter

[wilzbach]

There's currently an interesting discussion going on at the NG.

By accident among was compared between three doc engines:

DDox: https://dlang.org/library-prerelease/std/algorithm/comparison/among.html
DDoc: https://dlang.org/phobos/std_algorithm_comparison.html#.among
AdrDox: http://dpldocs.info/experimental-docs/std.algorithm.comparison.among.1.html

While they are essentially the same, I this is how the "out of the box" user experience looks like:
DDox (vanilla): http://files.wilzba.ch/dlang/ddoc_among/ddox/std/algorithm/comparison/among.html
Scod: http://files.wilzba.ch/dlang/ddoc_among/scod/std/algorithm/comparison/among.html

The biggest difference is that DDox essentially duplicates the documentation for every function and template of among. Ddoc and AdrDox group the overloads at the beginning and show the examples, parameters etc. only once.

[s-ludwig]

Fixed by #147.