New CDI scope @PortletSessionScoped that binds bean to the PortletSession

This is a code proposal related to the following discussion thread: https://www.liferay.com/de/community/forums/-/message_boards/view_message/40442240

I could not really test the code because I wasn't able to set up the whole build stuff on my local PC.

But I tested it within an extra Project - it worked well.