Polish logging in resource handling
ServletServerHttpResponse specifically checks for Servlet 3.0's HttpServletResponse.getHeader(String) method

Issue: SPR-11712
Polishing
General defensiveness about the bootstrap ClassLoader (i.e. null ClassLoader)

Issue: SPR-11721
Polishing
Rename Reactor support classes

This change modifies the names of the Reactor support classes in order
to align with the same changes in the 4.0.x line which now supports
both Reactor 1.1 and 1.0.

Issue: SPR-11636