Map HTML improvement

I just worked a bit over the 2D map generation and was able to reduce the size of the HTML significantly. Reload should be now much faster once the background image is in the browser cache. Also, the way the top-right coordinate and the region file of the area has been displayed is now much more visible.

A lot of the code that has been unchanged over the years is due for an overhaul and once I have time to look at a code and get new ideas how to solve a certain issue, we can get quite some improvements out of the system, luckily.