Expose a qform switch
Spit out non-linear brain mask for non-lin alignment

Up to this point only the linear component was applied to the
transformation of the individual brain masks.
Merge branch 'master' of medusa:/home/data/exppsy/forrest_gump/git/openfmri_code

* 'master' of medusa:/home/data/exppsy/forrest_gump/git/openfmri_code:
  Spit out non-linear brain mask for non-lin alignment
  Expose a qform switch
ENH: Specify an initial reference brain instead of using the closest to
the average.
ENH: Have a default working directory for nipype workflows
RF: Common option for input expressions
ENH: Common option to store workflow graphs
Ignore swap files in Git
Either graph execution or drawing
DOC: Clarify --label option a bit
NF: 'unwrap_phase command

Simplistic at present and needs more options.