Gwtii 210 integration merge to master with revert of plugin delete from master

Merging steps:
1) branch master and reset head to just before deleting the plugins (= GWTII-171 commits)
2) cherry pick the none-deleting commits on the master branch (= GWTII-173, GWTII-168, GWTII-189 and update .travis.yml)
3) merge integration branch (hardly conflicts)
4) remove graphicsediting plugin references (javadoc module) 

=> locally, mvn clean install is ok

Before this pull reqest can be merged into master branch, the three commits of GWTII-171 need to be removed from the master branch.

NEEDS VOTE