templatekw: allow accessing to nested namespace item by its template name
Since we have the dot operator, it makes more sense to write
{namespaces.tags % "{tag}"}
instead of
{namespaces.tags % "{name}"}
templatekw: rename peerpaths to peerurls per naming convention (BC)
Since each element is called as "url", the template keyword should be named
as "<whatever>urls".
{peerurls} is now stabilized.
templatekw: make experimental {peerpaths} return a single-level dict (BC)
This was planned as in
c0d8de2724ce, "{peerpaths.default.pushurl} will be
translated to peerpaths['default'].makemap()['pushurl'], which means
{peerpaths} should be a single-level dict and sub-options should be
makemap()-ed."