* Introduced NetworkViewRenderer interface to manage multiple renderers.
 * Introduced universal CyNetworkViewFactory that delegates to active NetworkViewRenderer.

Change-Id: Id058cb9f6bf56610083544d333cee9c77ef39c30
Removed AddDeleteHandler.  Completely redundant and consumed lots of memory.

Change-Id: I392f5ef2ec715e2fea04c09b41bbe5af90db415d
 * Cleaned up multiple renderer API
 * Decoupled core UI implementation from Ding

Change-Id: Id459b6596cba3c0b205a1aebda1d4b9f095862e9
Changed visibility of service listener methods so Pax Exam won't fail when we run session-impl integration tests

Change-Id: Ie65bbb4e57f59547ce36a75c915800683ba4fabd
Updated Visual Style preview UI to dynamically use current NetworkViewRenderer

Change-Id: If55158ffb1136ba0d5e16f9b4764fdb208d0148d
Added API for setting/getting default NetworkViewRenderer

Change-Id: I5ad01ec86db1b27722f2e3707b9505fcb49b6ef0
Revised and applied Yue's patches

Change-Id: I863c5ea05c23cb9e1f739c3b303513788484b1a6
Merge branch 'multiple_renderers' into develop

Conflicts:
	swing-application-impl/src/main/java/org/cytoscape/internal/CyActivator.java

Fixes #289: Added API/implementation for multiple renderer support

Change-Id: Iece3b7f4bf1d5dbdd298711d49f567005256070e