The test was comparing exact error message text, changed by previous fix to
include the transport error. Modified to check for a reliable substring.

container::schedule() with simple example of sending messages at a fixed interval.
Examples for C++03 and C++11.
Modified inject() to use the same proton::void_function0 as schedule for C++03.

Note: the example chains schedule() calls at a fixed interval. A precise
fixed-frequency sender should take account of the actual time to correct for
variations.

…ersions

- Make all member functions in container class pure virtual (except destructor)
- Add a new standard_container class that has the standard behaviour
  of the variant overloads
- Make all container implementations use standard_container class
- Remove unnecessary includes of container_impl

…is bound

Previously the reactor would be put on the transport's attachment list
when a socket selector was created for the transport.  If the socket
setup fails then no selector is created and the reactor is never added
to the transport.  This would result in a crash as the code depends on
the reactor being present in the transport when transport events are
generated.