Fixed "double-dot" extensions in output bin directory
When you install the NuGet package in a project and build, all the Mapnik files will be copied to the output bin directory. However all the files in the mapnik and share directories will have an extra dot in their names:

This change should fix that.
Sorry, I wasn't able to actually test my changes because I don't have .NET 4.5.2 specifically installed on my development machine. But I've done a similar thing for a separate project and I'm pretty sure this should fix the issue.
related with issue https://github.com/jbrwn/NET-Mapnik/issues/22
Not sure why the CI build is failing. It doesn't seem to have anything to do with my changes. Something about a mutex?
<mutex> is not supported when compiling with /clr or /clr:pure.
:+1: on the fix. I need the CI build to work before I can merge though. Ultimately, the CI build artifact nuget packages are what gets released on nuget.org.
Looks like the build is failing on the MSVC standard library patches. Not sure what is up with that. Unfortunately i don't have time time to debug this at the moment. If you can figure out what is going on i would gladly except your fix as part of this pull request. In the past i found the best way to debug this kind of thing is to actually login to the appveyor build worker.