show back icon when hovering over the header
show back icon when hovering over the header

instead of just when hovering over the button.
Hopefully this makes the button a bit more discoverable.

bagage/iD,edpop/iD,AndreasHae/iD,openstreetmap/iD,kartta-labs/iD,kartta-labs/iD,morray/iD,bagage/iD,zbycz/iD,1ec5/iD,digidem/iD,1ec5/iD,mapmeld/iD,tbicr/iD,AndreasHae/iD,morray/iD,energiekollektiv/openmod.sh-id,energiekollektiv/openmod.sh-id,digidem/iD,andreic-telenav/iD,andreic-telenav/iD,kartta-labs/iD,ngageoint/hootenanny-ui,ngageoint/hootenanny-ui,edpop/iD,bagage/iD,edpop/iD,mapmeld/iD,openstreetmap/iD,openstreetmap/iD,1ec5/iD,ngageoint/hootenanny-ui,tbicr/iD,kepta/iD,kepta/iD,zbycz/iD,AndreasHae/iD,mapmeld/iD