Merge pull request #602 from dengemann/lcmv_return_generator

ENH: allow for return_generator argument with lcmv epochs
WIP: add draft of gamma map implementation
wip gamma_map
gamma map method
gamma map cleanup
cleanup, moved mixed_norm
deprecated mixed_norm module
cleanup, renamed
update what's new
remove return_residual
option to return residual
Merge pull request #578 from mluessi/gamma_map

Gamma-MAP source localization method
attempted FIX:

COSMITS
ENH+FIX: truely delayed SSP