Refactor recalcAttrs

[rreusser]

Carpet is going to add a huge number of attrs to recalcAttrs. (up to 287 total or so!?) The array of attributes is recalculated on every plot and it looks them up with indexOf. It should place them in a hash (e.g. {mode: true, visible: true, ...}) and should be defined in a plot-api-global context since it never changes.

@alexcjohnson notes that a larger refactoring is desired, but this might be a start since, at least once carpet is merged, it shouldn't take more than five minutes and may very well be at the point of having a non-negligible impact on performance.

cc @etpinard

[etpinard]

Merging this issue with #648