Added BlockingQueue to DropController
Removed onDropEvent interface from DropListener
Added Javadoc to DropController
Merge pull request #95 from k-c13/uml-class-diagram

Delete core diagram img
Ignore the log directory
Merge pull request #98 from jasinai/IgnoreLogDir

Ignore the log directory
Merge pull request #94 from L-Henke/DropControllerWithBlockingQueue

Added BlockingQueue to DropController
ReceiveMessages returns a Collection<String>
retrieve() now returns a collection

* reformatted code
* removed unneeded method argument
synced test to new changed Drop methods
removed unneded import
Merge pull request #97 from jan-schreib/Multipart

Multipart
adding group to build.gradle
gradle: add settings.gradle to make the project work as child project
whitespace fix
Add method to load Class from Jar File
DropController: reintroducing the callback class
Adding DropQueueCallback class to mimic the Queue-behavior.
Add a receive function to the controller.
DropController: Retrieving DropMessages works