[1.1.4] VNCScreen::stop() should remove the related resources --- fixed 2018-12-28 build#158

[Rajarshi Poddar]

----------------- the below code is from version 1.1.3 !!!
----------------- the fixes are in 1.1.4
https://github.com/RaiMan/SikuliX1

---------------------------------------------------------

This piece of code below keeps the VNCScreen object in the HashMap.
https://github.com/RaiMan/SikuliX-2014/blob/develop/API/src/main/java/org/sikuli/vnc/VNCScreen.java
from lines 59:

public void stop() {
    try {
      close();
    } catch (IOException e) {
      Debug.error("VNCScreen: stop: %s", e.getMessage());
    }
    screens.put(this, null);
  }

Need a public api so that the VNCScrren Object can be removed from the cache when stop() is called.
Cannot use stopAll as the scenario where this is being used there can be mutiple VNCScreens and need to remove the specific VNCScreen object with disturbing or removing other VNCScrren objects.

Sikuli Version being used is 1.1.4. Operating system being used is Windows 64 bit.

Multiple creation of VNCScreen Object with same VNCClient. The hash map overflows ie the Java responds with out of memory exception.
To reproduce keep the max size of heap of java to be 1GB , create mutiple vncscreen objects with same client and run that in a loop of 1000000.