[DEBUG] #30 Permalinks deactivate layer visibility

Verifying that layers visibility is deactivated by permalink and set
visibility based on QGIS projetct.
[DEBUG] #18 Add a BBOX syntax for zooming

In addition to permalink and configurable initial extent, it's possible
to share link with bbox parameter.
[DEBUG] #29 Legend size bug with Chromium / Chrome

The width of legend images are different between Firefox and Chromium /
Chrome. This difference was due to bootstrap max-width css value.