Add a reasonable description for AbsolutePath and RelativePath.  It's not equal to `asString`, so it cannot be used for getting at the actual path, but is intended to be more readable than the default description, which is of the form:
Add a reasonable description for AbsolutePath and RelativePath.  It's
not equal to `asString`, so it cannot be used for getting at the actual
path, but is intended to be more readable than the default description,
which is of the form:

AbsolutePath(_impl: Basic.(PathImpl in _F37600050464D58680C1E5753557C388)(string: "/private/tmp/"))

which doesn't really help anyone.

The new form for the above would be:

AbsolutePath('/private/tmp')

sschiau/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,vmanot/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager,mxcl/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,mxcl/swift-package-manager,JGiola/swift-package-manager,JGiola/swift-package-manager,JGiola/swift-package-manager,haskellswift/swift-package-manager,vmanot/swift-package-manager,vmanot/swift-package-manager,mxcl/swift-package-manager,mxcl/swift-package-manager,JGiola/swift-package-manager,haskellswift/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager