Port play-cms to play framework 2.6.x
Created by: antonsudak
I want to introduce port of play-cms to the play framework 2.6.x versions. In this pull request following changes were made:
- updated dependencies to the most recent versions
- replaced deprecated in play framework 2.5 APIs with new analogs from 2.6
- replaced some of the deprecated in play framework 2.6 APIs
- rewrote attributes in order to remove http context usage in entities