Intentionally break backward compatiblity

[garfieldius]

The amount of workarounds and checks to support v7-v12 is difficult to maintain. Next major version, v7, should be TYPO3 v13+ only.

Steps included:

• Move all custom dependency fetching to DI
• Replace the USER cObject with a FLUIDTEMPLATE and
• Move logic from BannerRenderer userFunc to a DataProcessor
• Complete documentation of all TypoScript features and JS/TS interfaces, including DOM events fired.
• Optional: Rework the frontend JS/TS to be based on modules and plugins as described in Client side rework #23

[josefglatz]

related #39