Seeing funny behaviour where for nearly-Gaussian maps MELODIC changes the
value of `mmthresh`, making the combined maps inconsistent.
  However, the overall aim is simply to make the null of the DR maps `≈N(0,1)`.
Instead of using the full mixture model, we simply rescale the maps based on
robust estimators of the mean and standard deviation (i.e. that should be
relatively insensitive to the heavy tails).

Create a binary mask, and then multiply (i.e. rather than treating positive and
negative separately).
  Note that we also create `dr_stage2_${s}_thresh` maps now so these are more
readily accessible to the user.

Makes it easier to debug by leaving full mixture model outputs.

No longer seems needed - though a little unsure as to use in the first place???

The call to imglob seems to be altering the order of ICs. This removes the
combination of glob/imglob and replaces it with an explicit loop over ICs.

Cherrypick from master 2015-09-14 14:53:31 UTC Matthew Webster <mwebster@fmrib.ox.ac.uk> 'fix for tica/migp problem':
    dual_regression
    melgmix.cc
    melgmix.h
    melhlprfns.h
    melica.cc
    melica.h
    melpca.cc
    melpca.h

Sprout from master 2014-06-18 14:55:52 UTC Matthew Webster <mwebster@fmrib.ox.ac.uk> 'potential fix for weird child process bug on some accounts'
Cherrypick from master 2013-07-05 13:32:37 UTC Christian Beckmann <c.beckmann@donders.ru.nl> 'fixed f..... up calc_corr in econ mode':
    Makefile
Cherrypick from fsl-5_branch 2014-03-25 16:21:51 UTC Paul McCarthy <paulmc@fmrib.ox.ac.uk> 'Melodic exits early if specified time series/session design matrices do not match the data dimensions/number of input files.':
    meldata.cc
    meloptions.cc
Delete:
    doc/anim_gui.gif
    doc/concat_diag.png
    doc/gui.png
    doc/index.html
    doc/mel1.png
    doc/mel2.png
    doc/mel3.png
    doc/pica_diag.png
    doc/tica_diag.png
    dual_regression
    fsl_dualreg.cc
    melgmix.cc
    melgmix.h
    melhlprfns.cc
    melhlprfns.h
    melica.cc
    melica.h
    melodic.h
    meloptions.h
    melpca.cc
    melpca.h
    melreport.cc