Add a BE module

[oliverklee]

Goal

As a tea lover, I'd like to conveniently see all my teas in a BE module.

As a developer, I'd like to see a working example of an Extbase BE module and functional tests that I can copy from so that I can easily have well-tested BE modules in my own extension.

Acceptance Criteria

• We have a BE module "Tea".
• The BE module has the Tea icon.
• The BE module lists the tea records in the selected page in the page tree.
• The BE module shows the UID and title of each tea.
• If there are no teas, we have a corresponding flash message.
• The list is sorted by UID, highest first.
• The title and UID are linked to the TCEforms edit action.
• Going back from editing a tea shows the tea module again.
• We have a follow-up ticket for adding a full text search.