simplified a little bit of code in getFileGroup

doc tweaks.

Used by new gifti function relatedFiles

path looks like part of an incomplete file group.

when called programmatically.

the default file extensions (i.e. the FSLOUTPUTTYPE) - this is used by
the fslpy_immv/imcp command line scripts.

copies/overwrite errors. Made imcp overwrite check more robust.

dictionary. Intead, they use 'file groups', which is conceptually much
easier to understand. New functions splitExt and getFileGroup.

Also added imcp and immv functions, which perform the equivalent of the
FSL imcp/immv scripts (but are more general).

fsl.utils.path. Featresults get*File functions use addExt instead of
glob, as it is much more robust.

module. Hopefully fixed TimeSeries confusion w.r.t. nested
.feat/.ica directories