Pluto Portlet support for Flow

**EDIT 2: this about Portlet support for Pluto, using Portlet 3.0 specification. Portlet 2.0 support for other portlets like Liferay and/or Websphere will require additional effort (#5815 #5816) **

Current scope:

• Preparations for getting started with Pluto #6243
• Learn how to run integration tests with Pluto #6244
• Investigate differences between 3.0 and 2.0 spec vaadin/portlet-support#10
• Investigate how to preserve portlet state on refreshes vaadin/portlet-support#11
• Investigate how to create shared frontend resources bundle vaadin/portlet-support#12
• Prototype Portlet Mode support with a demo vaadin/portlet-support#20
• Investigate enabling PortletHub support automatically vaadin/portlet-support#30
• Investigate & Demonstrate Portlet window state support vaadin/portlet-support#26 vaadin/portlet-support#27
• Investigate IPC between Vaadin and non-Vaadin portlets vaadin/portlet-support#28
• Vaadin Portlet API proposal vaadin/portlet-support#25
• Address Book Portlet Demo vaadin/portlet-support#29
• Create base starter for portlets #6345
• UI state is preserved on refresh #6373
• Portlet support for Upload component #6374
• Multiple portlets on the same page from a single .war #6375
• Support portlet modes: edit & help #6377
• Portlet window mode support #6527
• Inter Portlet Communication support #6378
• Support CDI on portlets out of the box vaadin/cdi#116

Maybe:

• Automatic building of the frontend resources bundle #6376

[joheriks]

Portlet 1.0.0.beta1 release: https://github.com/vaadin/portlet/releases/tag/1.0.0.beta1

[rlegorreta]

+1. We urge to start a new Liferay 7.1 DXP project. We don’t want to use Vaadin 8 but Flow.