Create 3.x branch for Entity Processor

#1033202: [Meta] Generic entity processor has been open for more than 2 years w/ 200+ comments. A lot of progress has been made, but new issues continue to be added to a single issue. I'd like to suggest the current patch be used to create a 3.x branch and at least 1 developer interested in seeing entity processing get into the supported branch we made a maintainer or one of the existing maintainers agree to review new patches to that branch in a timely manner.

Thoughts?