Indicate last render date/time with span

I would like to know when the file gets re-rendered. I'm using this on a shared server and love the code, it does just what I need, I would just like to see when it was last re-rendered on my public page. 

Otherwise I love this project. Great stuff.

PS: I don't normally write in Java, so I'm sorry if I missed something >.<
Fix generation of date footer in tiles.html.
Merge https://github.com/TOGoS/TMCMR