[BUGFIX] EM: Colorpicker in extension configuration is broken

The colorpicker in extension configruation is broken. This is
because of missing images.

Also this fixes an issue with duplicate ID tags on a page. Which
causes some problem when CSS is defined on the same name.

Change-Id: I5c3b7005cd0f1df9399c0e1506bd8d408d661743
Fixes: #46021
Fixes: #46953
Releases: 6.1, 6.0
Reviewed-on: https://review.typo3.org/19616
Reviewed-by: Nicole Cordes
Tested-by: Nicole Cordes
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn