Major revisions to the class layout / data structure:
 * Introduced ImageDataConverter interface (still not really happy with the design)
 * Removed support for Int64 and double images from WeaklyTypedPointer
 * Added ImageDataGL::bind()
 * AbstractProcessor::init() method, gets called by AbstractPipeline::init()
 * added VisualizationProcessor

Updated/New processors:
 * fixed MhdImageReader
 * SliceExtractor stub for very simple slice rendering

Various fixes:
 * DataContaier: managing of DataHandle ownership
 * GenericImageDataLocal::getSubImage()
 * ImageDataRenderTarget bindings
 * GenericProperty
 * linking issues with StringUtils

Hence, all this enables the first usable implementation of a specific pipeline:
The SliceVis pipeline combines MhdImageReader and SliceExtractor for a very simple 2D slice rendering

git-svn-id: https://camplinux.in.tum.de/svn/campvis/trunk@188 bb408c1c-ae56-11e1-83d9-df6b3e0c105e