templater: make date wrapper support dot/map operations No idea if it will be useful, but it just works.

templater: introduce a wrapper for date tuple (BC) Strictly speaking, this is BC, but I believe the original string format (str(float(unixtime)) + str(int(tzoffset))) was just plain wrong.

templater: promote tomap() to an interface type I originally considered merging tomap() with itermaps()/getmember(), but decided to not. We might want to add support for chained map operations (e.g. {foo % func() % ...}), where func() will return a mappable object, and 'foo % func()' will be a mappedgenerator of mappable objects.