Allow displaying map for mix of trips with and without times; don't show transfer dots when there are no times, or if tag is a collection

I think these are related: 1. When displaying a map for a tag or list of trips, if it's a mix of trips with and without times, treat all as without times (and apply the two points below) and just display it instead of giving a 416 error; maybe show a small warning. 2. When displaying a map for a tag or list of trips without times, don't show transfer dots since they are meaningless: there is no order between trips. 3. When displaying a map for a collection tag, even if all trips have times, don't show transfer dots since they are meaningless for a collection. In "non-ordered mode", I think times and dates for individual trips that have them should still be shown in the side bar. But that's not a must. You wouldn't have date headers, just show the date (and year!) next to every entry the way it's now done for entries at the start of a day. Alternatively, you *could* still sort and display dated trips like now, and just sort all the the non-dated trips at the start or end, that would also be fine.