Modify copyFiles to allow recursive copying of directories with contents, if directory name is specified in file list (or matched by wildcard)

Implement copyDirs parameter, similar to copyFiles - should recursively copy directory content to destination

Put BuildSettings into its own module and invoke DMD to determine the actual build platform. ...

Currently only for DMD, the build platform is now determined by actually invoking the compiler with the proper -mX switches instead of guessing from the compiler run that was used to build DUB.