* Fixed bug introduced in 8a8f9bba: Mouse wheel handler was modifying wrong slices
* Updated README.md

To build CAMPVis using NMake one had to manually copy several external
DLLs into the CMake output directory. There were 2 reasons for that:
- our macros treated NMake as a compiler and didn't try to detect what
  compiler NMake will actually use; as a result, they couldn't find the
  right external DLLs for NMake-based builds
- Visual Studio manages build types independently of CMake and always
  outputs into a build-type-specific sub-directory of the CMake output
  directory — that's where we place external DLLs; NMake, on the other
  hand, relies on CMake for build type selection and will output
  directly into the CMake output directory; due to this discrepancy,
  NMake-based builds couldn't find the external DLLs that were copied
  into the build directory

As many popular IDEs (e.g. Qt Creator, Code::Blocks, Eclipse CDT) rely
on NMake to build projects on Windows, it makes sense to have a working
support for NMake in our build system.

Update our compiler detection macros and adjust the CMake output
directory to match that of Visual Studio when NMake is used to improve
the support for NMake-based builds.

* Fixed orientation of XY-slice (flipped along Y axis)
* Implemented background for raycasting result
* Fixed sum for volume rendering integral evaluation in simpleraycaster.frag

Beautifying VolumeExplorerDemo and VolumeRendererDemo sample rederings by fine tuning transfer functions.

Added s_propertyAdded and s_propertyRemoved signals to PropertyCollection signaling changes to the property list. PropertyCollectionWidget listens to them and updates the GUI on the fly.

* fixed shader (de)activation in AbstractTransferFunction::bind()

Merge branch 'fix-warnings' of /mnt/bigone/git/repositories/sebastian.poelsterl/campvis into development

Merge branch 'shared-libs' of /mnt/bigone/git/repositories/sebastian.poelsterl/campvis into development

* Fixes #362: assignment used instead of comparison
* slight update in GlMorphologyFilter

Affected classes:
- Columbia1
- AdvancedUsFusion
- StrainFiberRenderer
- SimilarityMeasure
- GeometryRenderer
- DataContainerFileLoaderWidget
- DataContainerInspectorCanva

Fixes enumeration value not handled in switch [-Wswitch] error

* Added assertion in ImageRepresentationGL constructor checking for matching number of channels

Removed deprecated setting of shader directives for geometry shaders in tgt::ShaderManager. This hopefully fixes GeometryRenderer single-pass wireframe rendering on non-permissive GPU drivers.

* Rearranged DataContainerInspectorWidget layout to use less space
* Added option to render custom channels in DataContainerInspectorCanvas

* Support read-out of texel values also for 3D images
* introducing tgt::Texture::texelAsFloat() for 3D images
* Fixed Qt crashes in FloatPropertyWidget caused by changing GUI from non-GUI thread