Bug 4671 pt4: refactor Format::assemble()

Bug 4671 pt4: refactor Format::assemble()

* replace the String local with an SBuf to get appendf()

* overdue removal of empty lines and '!= NULL' conditions

* reduce scope redux for many out assignments

* use sizeof(tmp) instead of '1024'

* Fixes many GCC 7 compile errors from snprintf() being called with a
  too-small buffer.

* update the for-loops in Adaptation::History to C++11 and produce output
  in an SBuf. Removing need for iterator typedef's and resolving more GCC 7
  warnings about too-small buffers for snprintf().