[FEATURE] Allow Backend Logo to be set via extConf

The Backend Logo can now be configured via extConf
and the Extension Manager.

The $GLOBALS[TBE_STYLES][logo] option has no effect
anymore.

Resolves: #74109
Releases: master
Change-Id: Id1c1975395b9163a0efbb0cf4dc9f402df2fcc3c
Reviewed-on: https://review.typo3.org/47026


Reviewed-by: Benjamin Kott <info@bk2k.info>
Tested-by: Benjamin Kott <info@bk2k.info>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>