DOC: typos
FIX: more reasonable file name handling

The expansion is now smarter and hopefully meets the POLS
Merge pull request #467 from dengemann/bti_fname_check

FIX: more reasonable file name handling
FIX: addresses #468 offset problem

Closes #468.
COSMITS
Merge pull request #469 from dengemann/bti_fname_check

FIX: addresses #468 offset problem
ENH: keep old ref_channels names

I erroneously renamed the ref channels according to a simple and
logical scheme that effectively blocks using adding the weight tables
using mne_creacte_comp_data and mne_add_to_meas_info.
Keeping the old name makes it less painfull to add the weights
ENH: drop low level reading
COSMITS
FIX: restore previous naming
Merge pull request #470 from dengemann/bti_fix_read

ENH: drop os low level file handlers

Just a maintenance PR, good to go.
ENH : sensitivity maps computation
more on sens maps
iter on sensitivity maps
update python ref
FIX: Fixing compatibility
STY: Alphabetical
STY: Grammars
ENH: More modes
FIX: Minor fix