Upgrade plugin to support Vaadin 8

Upgrade plugin to support Vaadin 8

0.7.3: Upgrade JUNG library from 2.1 to 2.1.1

Update to Jung 2.1.1

Change-Id: I17f0eae2ae76209325e36bb0dab0392d9f04f2d9

0.7.2: Upgrade JUNG library from 2.0.1 to 2.1

Upgrade the JUNG graph library to fresh 2.1 release which among others
updates its dependencies so collections-generic, concurrent and colt
dependencies are replaced by guava.

Change-Id: I723180a825046cf530de21aa79c444e09a135575