ENH:  KIT coregistration

 - allow setting coregistration parameters after KITRaw construction
 - add write_hsp() function
ADD: viewer module for HeadViewController, PointObject, SurfaceObject
OPT apply_transform: only transpose trans
ENH: add coord_trans() function for transform between different coordinate systems (ALS to RAS)
ENH marker_gui
ADD kit2fiff_gui
ADD fiducials_gui
update mne.gui: add fiducials()
ENH coreg: proper error message
ENH:  coreg / MRI scaling

 - scale_mri stores pickled params which can be read by read_mri_scale
 - ADD scale_labels function to scale additional labels for an already scaled
   MRI
 - cleanup
kit2fiff_gui
viewer
ENH: RawKIT.__repr__
ENH transforms: add rotation3d
ADD file_traits
marker GUI
ENH source_space: add mne_prepare_bem_model and mne_setup_source_space wrappers
ADD manual page
coreg_gui
viewer