The third incarnation of the monitoring internals. I'm not happy to c…

…ommit such big changes into the point release, but this is the only solution for the AST signal safety issues in POSIX (see CORE-2483).

The change consists of a few parts:
  - get rid of ClumpletReader/Writer classed and the related pool dependencies
  - replace a single huge clumplet for dbb with a set of smaller chunks
  - work with the dump at the record/field logical level
  - use the universal mover instead of manual tweaking with descriptors
  - automagical NULL handling instead of the hardcoded nullability rules
So far the testing hasn't revealed any functional or performance regressions.