Merge pull request #496 from dengemann/raw-plot-add-keys

ENH: plot_raw resp and ref_meg entries to color & scaling in dict
Merge pull request #497 from dengemann/raw-plot-add-keys

ENH: ... missing scaling + color dicts in raw.plot
WIP/ENH: apply_projection method as for Evoked

This PR moves the projection-activation to a private function and adds a new method
that allows to actiate the projectins later.

- This should make it easier to apply the projections late in the processing stream /
compare rejection effects etc.
COSMITS: add docstring, simplify expressions
COSMITS II
ENH: adding copy method
FIX: pass True
ENHL: implement oneway handling.
FIX/ENH: fixinf handling + adding proj option for read_evoked
ENH: ... actually adding the proj argument
ENH: set projn flag on creating aves
FIX: reference / copy bug
ENH: addressing points from discussion + COSMITS
ENH: adding add_proj
COSMITS
ENH: misc fixes + impriving the checking sequence + more readable