Make the conflict UI more useful and intuitive

[divec]

Summary
Implement the conflict UI shown here:

Understanding required

• The content we're three-way diffing (old MT, human correction, new MT)
• The three-way diff structure as returned by of ll.Differ#diff3 — see https://github.com/divec/ll/blob/master/tests/ll.Differ.test.js for examples
• How this would map to the UI above
• The linear model structure needed to power this UI
• What attributes we need in ll/conflict annotations

Changes needed

1. Rewrite ve.dm.LLConflictAnnotation to take the required attributes
2. Modify ll.adaptCorrections to return the required linear model structure
3. Write an inspector for ll/conflict annotations

[trevorparscal]

Segments belong to one of the following groups (and the colors as shown in the mockup above)

• context-original (gray)
• subject-original (black)
• context-change (light orange)
• subject-change (orange)
• context-merge (light blue)
• subject-merge (blue)

Conflicts are a combination of change and merge.

Design improvements:

1. Connect colors between timeline and document
2. Refine colors and coding to improve
   a. visibility
   b. accessibility
   c. relationship between segments
3. Improve labels to better guide the user