Fixed P2PDistance

Interface failed because tvtk is loaded with the default value
of ETSConfig.toolkit. Now it is initialized, so now the enthough.traitsui
does not look for $DISPLAY.
PEP8 formatting
[FSL] Updated BEDPOSTX and XFibres

Old interfaces are still available as OldBEDPOSTX and OldXFibres
fixed gradient nonlinearities implementation
fixed errors
fixed bug
fixed XFibres
fix doctest of BEDPOSTX
tested new XFibres. new parallel workflow
preparing new workflow for parallel processing
new split and merge interfaces
added test and some missing files in last commit
new parallel bedpostx finished :)
new naming conventions
Merge branch 'master' into enh/UpdateBEDPOSTX

Conflicts:
	CHANGES
	nipype/algorithms/misc.py
	nipype/interfaces/freesurfer/utils.py
bedpostx_parallel avoid computation of dyads uncertainty available
Interface Merge for large files
Merge branch 'enh/UpdateBEDPOSTX' of github.com:oesteban/nipype into enh/UpdateBEDPOSTX
fix missing comma
added computation of mean f samples in bedpostx