[REFACTOR] moved classes to Saros Core

Following files are not only moved but modified further

Removed Eclipse classes from TextSelectionActivity* and
ViewportActivity*

Extracted the QueueItem class out of the ActivitySequencer and put it
temporarily into the activity package.

Reasons why this patch cannot be made smaller:

At least following interfaces are needed:

IActivity, IActivityDataObject and ISarosSession

ISarosSession: depends on concrete classes StopManager,
JupiterStuff => *free movement* included for this patch

IActivity: depends on IActivityReceiver interface

IActivityReceiver: depends on all activities that currently exist in
Saros

all Activities depends on their marshalled counterpart !

Change-Id: I55b44cca417ac5a374011c67698dcaea09c6d018
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1431
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>