New tunable parameter to control gravity/order of tunables

Change-Id: I4fe1a6fac64983d948ea08ab3db3c840930021fa
Merge branch 'develop' into feature/gravityTunables
Modify javadoc comments

Change-Id: I79a69fffcc1994979868a263bdcb1f671aeb4dbf
Merge branch 'feature/gravityTunables' into develop
Merge branch 'develop' of git+ssh://github.com/cytoscape/cytoscape-api into develop