Be able to display a polyline instead of circles only

[srclosson]

Why?

1. Be able to use the latest version of leaflet
2. Strava has the capability of returning a polyline, strava will decode the polyline, but can also return the polyline in the dataframe meta if the panel wants to decode. Using this format allows the map to display the activity as a line, rather than circles. The circles may be better suited for tracking individual segments of an activity (ie: how much elevation did I gain in this last segment, or how high was my heart rate).
3. Currently, only the last activity was displayed. Changed to display all activities (or if an entry in a dataframes data section refers to an activity, use all activities defined in the dataframes data section.)

[CLAassistant]

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[amotl]

Dear Stephanie,

thanks for your contribution! May I humbly ask you to send this PR against [1]? This code base has been advanced to some amount and I will be happy to merge it. So, the community will gain more features on many levels.

Thanks already and with kind regards,
Andreas.

[1] https://github.com/panodata/grafana-map-panel

[srclosson]

Yup, will do :)