Added exception for tracks that are too long...

... for exporting.
Implmenented check for too long tracks...

... for shapefile export.
Created tests for shapefile export
Corrected c&p mistake
Fixed tests
Changes according to discussion:...

...
https://github.com/enviroCar/enviroCar-server/pull/195#discussion_r14128939
Merge pull request #196 from bpross-52n/issue-194

Issue 194