+ Adds basic client-side processing of label inference data structure
    - Minor restructuring of infinite_scroll_list.js to facilitate this
    - Still need to write full client-side inference algorithm
+ Displays inferred labels in yellow and blank labels in red

+ Moves the "more" button on trip cards to the top right corner
+ Adds a verify button beneath it that turns yellow labels green
+ Fixes a bug that mis-positioned trip start and end icons if labels were blank
+ Like the previous commit, does not affect the Diary page

+ This algorithm takes the list of label tuples and probabilities from
  the server and chooses which yellow labels to show the user, taking
  into account what the user has already begun to enter.
+ Extensively documented in the comments.

Testing done:
Tested various cases using the more extensive server-side placeholder
label inference "algorithm" recently committed.