Add topo scale feature for large mega macro topos to make features smaller

[brendanheywood]

From Julian S:

The belay/anchor points in the current topos are what I was talking about. Obviously you need to indicate the pitch ending, but the current 'dot' is huge. On a distant photo topo Perry's the dots and lines conceal quite a lot of 'wall space'. As such, you lose perspective and, moreover, any appeal the wall might have. For instance, there are now quite a few pitches to the right of Red Edge (Perry's Lookdown) at pitches 3, 4 and 5. (http://www.thecrag.com/climbing/australia/blue-mountains/perrys-lookdown/route/13161403). If I put them in it pretty much covers the entire wall; literally blanks it out.

The lines need to be about the width of the black edging of the current lines, or thinner, on both the distant and the zoomed in version.

• [ ] need to add topo field for storing a scale factor, most topos will be 1 but larger topos could be .8 or .5. This scale factor applies to all drawn features, effectively exactly the same as if the topo was made 2 times bigger and then responsively scaled down
• [ ] add atomTopo template data for scale
• [ ] add extra field to api endpoint for saving it
• [ ] wire in to topo JS (already working)