Display maps based on `.toc` files

[46bit]

• [x] Filter out controls from the TOC. These seem to be the ones where LAYER(name, caption, [...]) has a non-integer name.
• [x] Load TOC in the browser using the toc2json classes.
• [x] Rebuild the toc2json classes to build sources, groups and layers for OpenLayers.
• [x] Have a map displaying a TOC. Use ol3-layerswitcher to temporarily display and toggle layers.
• [x] Have layers selectable/unselectable at will.
• [x] Be able to display any map+TOC, in identical fashion to past query strings.
• [x] Use coordinates from past query strings.

[46bit]

Split many issues from https://github.com/46bit/arcims_migration/issues/17 into here.

[46bit]

Split remaining, nontrivial points into their own issues.