Long Track Pieces do not Show when First Coordinate is not in View

[Daniel-Gill]

An unintentional side-effect of pull #14.

The code for drawing the lines uses the first coordinate in the list to determine if the line is in view. This should be changed that all coordinates in the line are checked against the map bounds.

Example:

Moved slightly further North, and the line appears:

[Daniel-Gill]

I've added a few lines to solve the problem initially in pull #18.

I'm not closing this issue yet, as this is very inefficient.

[Daniel-Gill]

Maybe a better option to find whether a line is in view is to imagine a straight line between the first and last points, and check whether that line intersects the view.