Fix more collapsible leg issues

[graue]

PR to PR #324 implementing most of my feedback to that PR.

• Localizes the mode name labels by reusing code from RouteLeg
• Fully localizes the list of streets ("via Valencia Street, 14th Street")
• Removes useless use of async/await
• Removes unused viewingLeg member of routes reducer
• Fixes setState in render
• Allows expanding multiple legs at a time
• Misc cleanup

Not implemented because didn't seem blocking: Suggestion to use CSS to set the size (number of lines) of clamped alerts, using overflow: hidden and text-overflow: ellipsis, instead of a character limit

[graue]

for posterity: we did some testing and found that this branch removes much of the slowdown for some reason (possibly related to not rendering twice because of the render call in setState being removed). We think it's shippable now, although there is a bit of stuttering on @abhumbla's phone.