The RtfMemoryCache is an RtfDataCache that keeps the whole rtf document
data in memory. Fast but memory intensive.
version: $Id: RtfMemoryCache.java 2776 2007-05-23 20:01:40Z hallm $ author: Mark Hall (mhall@edu.uni-klu.ac.at) author: Thomas Bickel (tmb99@inode.at)