8 more road editor tweaks: copy, buttons, layout, hiding things

[X] Better errorcopy
- "(disabled: graph with errors!)" -> "Ill-defined yellow brick road!"
- "(disabled: new road is easier!)" -> "Road can't be easier within the akrasia horizon!"
- "(disabled: new road causes derailment!)" -> "Submitting this road would insta-derail you!"
- the huge red "road can't get easier!" on the graph is now just "Error" since the above errorcopy next to the submit button clarifies it
[X] Better instructions up top (and don't format it as single-item bulleted list)
- "Drag dots, vertical lines, or the road to edit, double-click to add new node" -> "Drag the bright red line (AKA yellow brick road) or double-click for new segments!"
[X] Hide the checkboxes for "show data", "show all data", and "show context graph" -- what madperson wouldn't want those things?
[X] Bullet-ify and label the road editing macros: ratchet, take-a-break, and road dial
[X] Make the fields less excessively wide
[X] Other spacing/layout tweaks -- space next to buttons mainly
[X] Call the road dial button "dial-it-in" instead of "UPDATE"
[X] New label for the remaining checkboxes: "Road-dragging behavior"

beeminder / road