MRG : EEG Reference reloaded !

Fine. Referencing Epoch objects it is.

-1 for dropping projections. The user has gone through the trouble of creating them, so we can assume he/she wants to use them. I would like to apply them instead (with an info message).

When I'm back at work, I can make the modifications to this PR. I'm thinking of modifying the functions to take either a Raw or Epochs object as first argument (rather than creating even more referencing functions).