Issue 6728:	Performance impact of dataTable lazy loading export feature

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null check

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@10924 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c
Custom filtering feature via filterFunction

git-svn-id: http://primefaces.googlecode.com/svn/primefaces/trunk@10925 5a70e874-a5cb-11dd-8af2-493fb0bb9f7c