The source for the module instance needed by any service builders, service contributors and service decorators that
are mapped to instance methods.
Allows the creation of the module instance to be deferred until actually needed; in practical terms, when the
builder/decorator/contributor is a static
method on the module builder class, then a module instance is not
needed. This allows Tapestry IOC to work around a tricky chicken-and-the-egg problem, whereby the constructor of a
module instance requires contributions that originate in the same module.
The term "module builder" has been deprecated; the current term is "module class", but this interface is left as-is
for backwards compatibility.