allow python configurables to add themselves to EventLoop job objects

The ultimate goal here is to have the python configurable no longer
inherit from the C++ object, and instead create the C++ object only at
the moment when it is needed, instead of having it as a base class and
performing all updates simultaneously to the python object and the C++
object (to keep them in sync).  However, for now it mostly adds an
alternate way of adding algorithms to jobs, to actually make the more
fundamental change to the configurables would require all users to
update to the new formalism of adding algorithms to jobs.

This also allows additional configurable objects to be used, e.g. I
now treat algorithm sequences and algorithms the same.

This could potentially also be used to change the target or mechanism
of configuration at some point, e.g. to push this into an intermediate
JSON file, but that's not an immediate goal.