Merge pull request #647 from dengemann/magnes_layouts

ENH: magnes improvements pt 1
enhancements to topo plotting
ENH: refactor code
COSMITS + FIXES + improve test
FIX: fix topomap example
ENH: add delayed SSP

- 'works' but for some reasone I don't yet understand the
figure does not update
FIX+REFACTOR delayed SSP
COSMITS
ENH+API: refactor, improve code, doc + debug
FIX: revert previous layout edits
update what's new
ENH: add tick control
COSMITS
COSMITS
ENH: onpick
ENH: make @agramfort's line perception happy
ENH: improve vline, address discussion
FIX type handling
ENH: add layout guessing, address discussion