Merge pull request #6056 from riadvice/big-image-conversion

...bluebutton/presentation/DocumentConversionServiceImp.java

...ain/java/org/bigbluebutton/presentation/ImageResizer.java

...va/org/bigbluebutton/presentation/SupportedFileTypes.java

...bluebutton/presentation/handlers/ImageResizerHandler.java

...a/org/bigbluebutton/presentation/imp/ImageResizerImp.java

...n/presentation/imp/ImageToSwfSlidesGenerationService.java

...ton/presentation/imp/PdfToSwfSlidesGenerationService.java

bigbluebutton-web/grails-app/conf/bigbluebutton.properties

bigbluebutton-web/grails-app/conf/spring/doc-conversion.xml