Fixed warning

Create the results.townsprimary-index only if it does not already exist
analyse: calculate times for townextract

this is like the times for boundingboxes but for townextract-data insted of boundingbox-data. The timetable is a bit redundant because the entertime of one box is always the leavetime of the previous box, but so it's easyer to port the visualise-code.
ported visualise to townextract

fixes #2
visualise: Added name of the border as hovertext
Visualise-townextract: reduce SVG-filesize by using CSS

For the testdata this reduced the filesize from 1.2 MB to 715 kB without altering the apperance in google chrome
visualise-townextract: changes to size and position of hover-text