panels 8.x-3.0-beta4

This release of panels is mainly to address IPE UI enhancements and resolve some outstanding bugs.

Changes since 3.0-beta3:

• #2663530 by dsnopek: Update for move of page_manager UI's to page_manager_ui
• #2662974 by dsnopek, japerry, phenaproxima: Move Panels-specific code out of Page Manager
• #2667648 by dsnopek, japerry: Add the PanelsTest back
• #2667694 by dsnopek: IPE using invalid entity operation 'write'
• Normalize some of our panels_ipe CSS rules that depended on default Bartik styling.
• #2659546 typo on merge
• #2659546 by phenaproxima: Add special 'change layout' op to access checking in PanelsStorage
• #2636532 by samuel.mortenson, japerry: Previewing a Block containing a Form in the IPE breaks add/update
• #2665716 by samuel.mortenson: Address the simple IPE issues from #2662354
• Remove panelstest because it requires page manager ui, which doesn't exist yet.
• Revert "Add page manager ui to the test dependencies as well."
• Revert "Try tests with only page manager ui"
• Try tests with only page manager ui
• Add page manager ui to the test dependencies as well.
• #2666232 by dsnopek: Add page_manager to test_dependencies
• Add a default value when getting the context mapping from Form state in PanelsIPEBlockPluginForm::submitBlock().
• #2664614 by phenaproxima, dsnopek: Add a setter to PanelsDisplayVariant for setting the page title
• #2665332 by dsnopek: IPE not saving context mapping (and trying to map contexts too early)