Release 7.4.0: Changed defaults and added properties for preview cache

[Guest]

Changed the default value of property com.openexchange.preview.cache.quota in preview.properties from 0 to 10485760 (10MB).
com.openexchange.preview.cache.quota=10485760

Changed the default value of property com.openexchange.preview.cache.quotaPerDocument in preview.properties from 0 to 524288 (512KB).
com.openexchange.preview.cache.quotaPerDocument=52 4288

Added option com.openexchange.preview.cache.type to preview.properties to specify where to store preview cache data. Possible values are file store (FS) or database (DB). Default is FS (file store)
com.openexchange.preview.cache.type=FS

Added option com.openexchange.preview.cache.quotaAware to preview.properties to specify if stored data should affect quota or not. Only applies if com.openexchange.preview.cache.type is set to FS Default is false.
com.openexchange.preview.cache.quotaAware=false