[Merkaartor] Osmarender integration

[bvh]

Just checking it out. It needs some basic error checking which
I am going to add right now.

However I think we also might want to include some stylesheet
inside merkaartor so that there is no need to install anything
extra. We could always provide an option for advanced users
to select their own stylesheet.

So what is needed from osmarender? Can we include it through
svn:external? Can we then include it in our resources?

cu bart