Updated logback-test file
Added support for following methods for files of type directory: 
getLinks: returns an empty array; 
getTags: returns an empty array;
getMedia: returns null;
creationTime: returns null;
lastModifiedTime: returns null
lastAccessTime: returns null
fileKey: return the directory path;
getTypes: returns an empty array;
size: returns zero;
isSymbolicLink: return; false;
isOther: returns false.
DxPath implements equals and hashCode methods
Fixed tests
Added parameters validation
Updated Gradle version
Updated version number