The 2.x branch enables a data property used to store any settings associated with a view, such as show/hide pager or number of results shown. It uses a Plugin Manager to add settings to the views reference fields and enables site builders to hide provided settings for each field instance. The branch itself comes with some settings and developers can add more through custom plugins.
The only significant change here is the addition of the advagg_bundler sub module to the 8.x-3.x branch. It is ready for use with all the same functionality as in 8.x-2.x (and 7x).
Also, quite a few bug fixes. Thanks everyone for the reports, testing and discussion.