dsynth - Add Dynamic memory load management

dsynth - Add Dynamic memory load management

* In addition to using the load and swap, also use the total
  estimated installed package dependencies for each worker verses
  PhysMem and reduce the number of worker slots such that this
  total is less than 1/2 physical memory.

* Fix a ^C handling bug where dsynth would try to unmount while
  still holding a file descriptor open on the filesystem it is
  trying to unmount.

* Clean up the logs a bit more.