Slicetiming, modular tasklists

Fixed problems in slicetiming
Renamed dicom header stream in aamod_convert_epis to conform to other
header stream conventions ('t1_dicom_header', 'structural_dicom_header')
Added modular tasklists via aas_generateRecipe.m and
aap_tasklist_begin.xml and aap_tasklist_end.xml
Modularised aamod_firstlevel_model script

Original one was bulky and unwieldy, and given that we have several
different ways of doing firstlevel (like Mumford/Poldrak) that are not
(yet) readily placed in a single module, it will be easier to debug if
the machinery remains constant across aamod_firstlevel_model variants.
Added extrafunctions from sasha branch

A bunch of useful extrafunctions
Also fix aamod_convert_epis to save info on slicetiming and TR
Added ANTS modules

Modules using the ANTS toolbox
(still may need to add parameters to find ANTS directory, etc.)
Added a set of useful, fairly stable modules (biascorrection, segmentation, ggmfit, normalise, smooth, secondlevel permutation, GLMdenoise)
Added freesurfer based modules
Fixed meanepi stream in modules to be a subject stream, not a session=1 stream
Fixed meanepi stream in modules to be a subject stream, not a session=1 stream
Last fixes and additions to share-devel...

Tested them with a simple 3T dataset for the core functions. Errors in
more esoteric/novel functions may remain.
Will test this in the coming weeks and fix where appropriate.

Notes:
Corrected aas_garbagecollection (here varargin is not appropriate since
we also include output permancence threshold, which is numeric)
Renamed spm_render to spm_render_aa to avoid conflicts elsewhere.
Improved some graphics in aamod_firstlevel_threshold