Raise DocumentCache hard cap to 512MB
Raise DocumentCache hard cap to 512MB

Soft cap is still 40% of available memory on startup.

NiLuJe/koreader,koreader/koreader,koreader/koreader,Frenzie/koreader,poire-z/koreader,poire-z/koreader,Frenzie/koreader,NiLuJe/koreader