Add basic Path finding utilities

[ajlake]

Maybe something like (or as methods in MoreFiles):

public final class PathFinder {

public static Path find(String relativePath) throws IOException {
    return find(Paths.get(""), relativePath);
}

public static Path find(Path basePath, String relativePath) throws IOException {
    Path currPath = basePath.toAbsolutePath().normalize();
    while (currPath.getParent() != null && Files.notExists(currPath.resolve(relativePath))) {
        currPath = currPath.getParent();
    }
    if (Files.notExists(currPath.resolve(relativePath))) {
        throw new IOException("Could not locate " + relativePath); 
    }
    return currPath.resolve(relativePath);
}

}