Webserver: add access to special:// URLs 

This adds a new HTTP handler allowing for special:// vfs files.
Access works analog to VFS via http://xbmchost:port/special/special://path/to/file
It also adds a shortcut URL /log for quick and easy xbmc.log downloading.

.log and .xml files are passed through a User/Pass stripper before download:
   - username:pass in URIs
   - <pass>pass</pass> in XMLs

I added VS2020 project files, but _did not test_ them. 
Since Xcode stuff is voodoo to me, I kindly ask someone in the know to help there.