Don't XML encode entities in the project paths when reading an Xcode workspace

Get the raw value of the location attribute instead of using to_s, which encodes entities. This fixes issues when an Xcode project path contains characters that would otherwise be encoded as an XML entity such as an apostrophe ('). While it is likely more "correct" to encode these entities, Xcode doesn't do it nor does it decode them, resulting in broken projects in the generated workspace with names like "Otto&apos;s Antenna".