BC: let the contianer return a Webforge\Framework\Project instead of an Psc\CMS\Project
add a dir() method to Project Interface which returns the semantic directory locations of a project
implement it in the SimplePackage (to make it also avaible to projectPackage)
introduce the DirectoryLocations to find the actual locations
refactor the InstallerParts TestCases to use the ACME\SuperBlog package as root and use vfs for the root