Very rudimentary help for the beginning world-builder.
Help links in build pages.
Add a stub documentation page.
Session-list admin page.
Templates for the admin sessions page.
Admin players page.
Split out the admin handlers.
Better error message when the web socket fails to open for no reason.
Support multiple assignment

>>> a = 1
>>> b = 2
>>> c = 3
>>> a = b = c = 4
>>> a
4
>>> b
4
>>> c
4
Add tuple support to execcode_expr_store.

Returns a tuple of BoundProxy objects suitable for assigning to.
Support assigning to a tuple.

>>> a = 1
>>> b = 2
>>> c = 3
>>> a, b, c = 4, 3, 2
>>> a
4
>>> b
3
>>> c
2

This is not neat, I get the feeling there should be some way of
handling this without setting each value individually, but this does
work.