templates: make earlycommands and othercommands optional
We now have sub-topics in the help system. The "helptopics" template
serves as a mechanism for displaying an index of help topics.
Previously, it was only used to show the top-level list of help topics,
which includes special groupings of topics.
In the near future, we'll adapt "helptopics" for showing the index
of sub-topics. In this patch, we optionally render {earlycommands} and
{othercommands} since they aren't present on sub-topics.