Box Plot: Fix keyAccessor, extent filtering, x domain change

[mtraynham]

This fixes the data binding between the g.box SVG nodes and datum keys. It should be using the keyAccessor, but it just happens to work here because Crossfilter always has datums with a key field. There are a few other places dc does this...

This also fixes filtering with X domains that are not ordinal and use brushing. The issue can be seen in the examples page, here.

[mtraynham]

Seems my own commit suffered from incorrectly accessing the datum's keys... fixed 😄

[gordonwoodhull]

Yeah, a few places.

$ grep \\.key\\b src/* | wc
      33     204    2432

😦

Thanks, this is really helpful!

[mtraynham]

33 that's not so bad. Maybe a few are in comments.

[mtraynham]

One more change I've added to this. If the x domain changes, the new width is only applied to the enter nodes. Older nodes retain their old width. Simple change.

[gordonwoodhull]

Thanks @mtraynham! Merged for 2.0 beta 33.