trailing slash for model urls
connect upload view to api
introduce gpx import exception
need to use multilinestring instead of linestring.
complex routes that intersect cannot be stored as simple
linestrings and trying to convert multilinestrings to linestrings might
introduce new issues
add migration for field change and docstring for api resource
adapt length calculation for multilinestring
adapt calculations to use the multilinestring object and fix length
calculation by using a generator.
fix bugs related to change to multilinestring and introduce function to
get approximate earth radius for given latitude
update mapview to correctly render multilinestring