To increase automated testing to support some of the larger PRs (processing#5753), moved some image and input logic to strategies under a new core.util module so that they can be unit tested without testing with a full PApplet. Will soon refactor out other places where java hits some of the more systems oriented calls like read bytes and create output as well as image save logic for consistency. Tests and JavaDoc pending.

Re-introduced base 64 image loading tests from image path despite the rollback of sampottinger/processing #3. There were some issues with the API migration earlier and would like to leave this in if possible.

Revert of sampottinger/processing #3 for the antlr branch.

Revert of sampottinger/processing #3 for java11 branch.