[TASK] Cleanup "beuser" sysext

This is a non-functional change that reformats the code, removes
unnecessary empty lines and fixes namespaces in phpDoc. In addition
the following to changes are made:
- add $GLOBALS['TYPO3_DB']->sql_free_result() calls to free some memory
- change bu:SpriteIconForRecord to bu:spriteIconForRecord in templates

Change-Id: I6e832921c46f828c9db0c796d662bd8390b5ac5f
Resolves: #45343
Releases: 6.0, 6.1
Reviewed-on: https://review.typo3.org/18190
Reviewed-by: Oliver Klee
Reviewed-by: Markus Günther
Tested-by: Markus Günther
Reviewed-by: Stefan Neufeind
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader