Add support to limit the size of the cache.
Reference: https://groups.google.com/forum/#!topic/mayan-edms/yM0_Ecekg3g
Create a new common app model called CacheFile that replaces documents.models.DocumentPageCachedImage. Store the cache file size to allow easier total size computation using the Sum annotation. Store the datetime added to determine the oldest files to delete first. Last datetime of access if the idea variable to determine oldest cache files but required a database write on each access.
Edited by Roberto Rosario