templatekw: hide {peerpaths} keyword for 4.3 Thinking a bit further about list/dict subscript operation (proposed by issue 5534), I noticed the current data structure, a dict of dicts, might not be ideal. For example, if there were "'[' index ']'" and "'.' key" operators, "{parents[0]}" would return "{p1rev}:{p1node}", and we would probably want to write "{parents[0].desc}" to get the first element of "{parents % "{desc}"}". This will basically execute parents[0].makemap()['desc'] in Python. Given the rule above, "{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. "{peerpaths % "{name} = {url}, {pushurl}, ..."}" (Well, it could be peerpaths['default']['pushurl'], but in which case, peerpaths['default'] should be a plain dict, not a hybrid object.) So, let's mark the current implementation experimental and revisit it later.