[TYPO3-v4] Refreshing the sprites of the new BE skin

[Steffen Ritter]

Hi,

first, no sprites are generates, all sprites are shipped, so no 
imagemagick needed

second, an installation updating does not have a sprites folder, so 
cache will be generated

so this is currently just an problem for developers working with 
different snapshots. What helps out, deinstall help extension :)


Reasons why this is not bound to backendcache:
- files are written, and calculated - this is only needed wenn new icons 
are registered or extension list changed
- if you configure your install to GENERATE sprites (in contrast to what 
is default) images would be generated ever and ever - even if they won't 
change (for weeks).

This behavoiur of non clearing cache, also just applies to CORE ICON 
CHANGES, since they are not covered by the detection...

Resüme: blank installations and udpates wont have problems...