API: .vertno -> .vertices
Merge pull request #1705 from christianbrodbeck/API/vertno

API: .vertno -> .vertices
ENH: specify ncov rank
Finalize #1709
Update whats new
Merge pull request #1711 from dengemann/enh_inv_ncov_rank

ENH: inv ncov rank
Add more referencing options

This adds a base function 'apply_reference' that can apply various
different referencing schemes. Two convenience functions are also
added that provide a convenient interface to the base function:

 - set_eeg_reference: apply a simple reference to all EEG channels
 - set_bipolar_reference: apply a bipolar reference (or more)
Add flag that a custom reference has been applied

Raw and Epoch classes will no longer add an average reference if the
`custom_ref_applied` flag was set. SSP projections will still attempt
this, but a new assertion in `make_eeg_average_ref_proj` will raise an
error if the flag was set.

Before a CAR projection is added, the `info['custom_ref_applied']` flag
is checked.
Add default channel name for bipolar references

- Also check for duplicate channel names
- Bilpolar channels can be named after the anode/cathode
- Inform user of the chosen bipolar channel name
Updating ref and what's new
Some improvements to the docs
Make apply_reference a private function