Windows installer does not register plugins

I just downloaded a Windows installer from a recent Appveyor build (2.41.20180302.1211) and the first time I ran dot.exe with arguments, including -Tsvg, it told me that svg was not a supported output type. I then ran dot.exe without arguments, and got an error message suggesting I run dot -c as an administrator to register plugins. I did this, and then I was able to render graphs.

The Windows installer should run this command during the installation process to improve ease of use.