add offline functionality by making this a PWA

- added favicons
- added manifest
- split javascript into main.js and elevators.js

icons/favicon-transparent.svg

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   width="100mm"
+   height="100mm"
+   viewBox="0 0 100 100"
+   version="1.1"
+   id="svg1"
+   xml:space="preserve"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg"><defs
+     id="defs1" /><g
+     id="layer1"
+     transform="translate(-214.49603)"><path
+       d="m 248.06205,71.319802 h 10.65991 V 57.1066 h 3.55325 v -8.883247 q 0,-2.931469 -2.08753,-5.019037 -2.08752,-2.087555 -5.01898,-2.087555 h -3.55339 q -2.93146,0 -5.01898,2.087555 -2.08753,2.087568 -2.08753,5.019037 V 57.1066 h 3.55325 z m 5.33002,-33.756351 q 1.8654,0 3.15345,-1.288052 1.28792,-1.288051 1.28792,-3.153558 0,-1.865479 -1.28792,-3.153545 -1.28791,-1.288051 -3.15345,-1.288051 -1.86553,0 -3.15358,1.288051 -1.28792,1.288052 -1.28792,3.153545 0,1.865493 1.28792,3.153558 1.28791,1.288052 3.15358,1.288052 z m 13.94658,8.883247 h 17.76655 l -8.88328,-14.213184 z m 8.88327,21.319804 8.88328,-14.213198 h -17.76655 z m -35.53296,17.23349 q -4.70808,0 -7.95044,-3.24238 -3.24249,-3.24238 -3.24249,-7.95051 V 26.192898 q 0,-4.708124 3.24249,-7.950507 3.24236,-3.242383 7.95044,-3.242383 h 47.61427 q 4.70809,0 7.95044,3.242383 3.24236,3.242383 3.24236,7.950507 v 47.614204 q 0,4.70813 -3.24236,7.95051 -3.24235,3.24238 -7.95044,3.24238 z"
+       id="path1-3"
+       style="fill:#000000;fill-opacity:1;stroke-width:0.0888325" /></g></svg>