skip refreshing assets cache while no database is configured

fixes cc before setup finished
Merge remote-tracking branch 'vivid/3.6' into 3.6
also pass config files writeable check if folder is writable
corrected spelling errors in trl.xml
silently ignore apc_store returning false

this silently ignores the "Failed saving metadata to metadataCache" exception when apc is used.
Merge branch '3.6'