Introduce the non-daemon process pool as an alternative to the original multiprocessing pool. This adds support for hierarchical multiprocessing (child classes can use multiprocessing again).

The code is based on the following StackOverflow answer:
http://stackoverflow.com/a/8963618/1183453
Add the non_daemon option to execute the MultiProcPlugin nodes as non-daemon processes.
brk: adding save changes
Merge branch 'master' into enh/saveworkflow

* master:
  changelog
  DOctest fix
  PEP8
  add doc
  DOC: Update info on Condor and its plugins.
  DOC: Fix documentation glitch
  BF: Use unique filenames for DAGMan workflows
  enh: remove logger dump added in 9d6b1a86921982b84f17b75ebf1a515f1d8710f7
  fix in NewSegment warp field output options
  fix: ensure that commandline calls force terminal output if stdout or stderr is required
  fix: failing flirt test
  fix: doctest for commandline
  doc: added change note
  enh: allow commandline interfaces to control terminal output
  adding trim interface that keeps the original dtype storage
adding missing options to interfaces.afni.Resample
brk: still updating export
added dilation file Rfor fMRI
corrected formating issue
build label files only for scale you want parcells for
added some needed code for the dilationl
added files to interface output
Merge remote-tracking branch 'upstream/master' into enh/saveworkflow

* upstream/master:
  added maths.MaxImage examples
  test maths.MaxImage for fslmaths -Tmax option
  add maths.MaxImage for fslmaths -Tmax option
  fix: change type of loops,speedup and between loops so its compatible with changes in the nipy code
enh: first pass at saving a flattened workflow to a python file
fix: attempt to resolve pickled function strings
fix: update a few more dynamic interfaces and allow for keyword arguments to be encoded
fix: datagrabber outfields
fix: node names should reflect workflow heirarchy
fix: node.name still being used
fix: node.name still being used
fix: node.name still being used
fix: nodenames in connect statement