red-brick: Prefer ISO8601 like date/time format
red-brick: Workaround signal emit problem when REDProgram is created in the async thread
red-brick: Fix typo and logic in REDProgram wrapper
red-brick: Improve reference handling for RED Brick API objects

Replace REDObject.__del__ with REDObjectReleaser that uses a weakref to
be notified when the last reference to a REDObject got removed to release
the unterlying RED Brick API object. Now the Python GC can break cycles
again, which was hindered by the __del__ method before.

Make the REDBrick callback registry only keep weakrefs to the callback
function. Now registered callbacks don't keep REDObjects alive anymore.

Also drop dead weakrefs to callback functions on each pass of callback
dispatch.
red-brick/pi: Add status display
red-brick: Use unicode() instead of str() if data can be non-ASCII