Add kernel.cache_clearer and/or kernel.cache_warmer support

[gena01]

Please add support for either cache_clearer or cache_warmer. This will resolve a number of issues as well as providing a way to warm the cache and catch any serializer mapping errors during app/console cache:clear

[leafpeak]

+1

[rande]

One of the reason is that JMS can serialize anyclass. So the solution will be to create a dedicated cache warmup (for doctrine entities).

[goetas]

Symfony is going to remove the cache:clear command since nobody was using it.... if you need to remove the cache.. just do rm -rf carchedir