Durable Fully Printable Customizable Spring

My [previous printable spring](http://www.thingiverse.com/thing:1758631) has an annoying tendency to break, this is the result of me trying to solve that problem.

In this spring every layer is made out of continuous and long strands of plastic, this makes it very strong and durable.

When printing set your shell width to at least half of the spring's lines (outerRadius minus innerRadius in the customizer, 2mm in the STL) this will make the spring all shells and that is what makes it work.

I tested it in ABS and PETG and it worked really well (PETG seems to be more durable), didn't try with PLA yet.