fixed bug in core api: desctructor of Runnable does not account for a missing call to start() before destruction

moved matrixprocessor to base module; removed obsolete positiondata.h and transformdata.h from openigtlink module; fixed include statements;

matrixprocessor now listens for dataAdded signals of the data container. also, documentation of the MatrixProcessor class.

contains processing of IMAGE and TRANSFORM messages

Itk reader

ITK Image reader that supports many more image formats.
Example usage edited into the itkfilterdemo pipeline.

 * supports all file formats that can be read via ITK
 * does not support image series

* SliceExtractor FitToWindow property defaults to true to mimic old behavior per default
* PointPredicateRenderArea renders y axis label

* Now supports optional scaling and offset of image
* Added properties for geometry render style and size
* Fixed some scribbling-related bugs

Slice extractor scribbe fix

as discussed

Datastructures

basic datastructures for Matrix and position data

Slicerenderer2d

slice renderer that applies transfer function, clips image and/or inverts axes.
tested only with grayscale input images, but should support color and images as well.

* undo changes to .gitignore (regarding SWIG temporary files)
* moved implementation of PositionData and TransformData from header to source file

Mhdreader fix

Sorry for the huge commit - only couple of files changed (see commit) :-(

Fixed timing issue in CampVisPainter that led CampVisPainter::paint() being called before CampVisPainter::init(). CampVisPainter::paint() now ensures the class (and in particular the shader) to be correctly initialized.

fixes #564

Initial implementation of a Lua scripting layer

Over the last several months a scripting layer that allows pipelines to be defined in Lua has been developed. It uses SWIG to generate Lua modules with bindings for CAMPVis classes. It is an opt-in feature, and tries to be as non-intrusive to standard CAMPVis code as possible.

The implementation of the scripting layer has reached a state where it's possible to write fully-functional pipelines in Lua. In fact, 2 existing pipelines have been reimplemented in Lua for testing purposes and added to the project. In my opinion, this marks a good point to merge the initial implementation into the development branch — that would make it easier to test and improve it.

Naturally, there are still many rough edges that should eventually be dealt with, but they can be addressed separately as new features:
- bindings coverage is rather low
- Lua pipelines currently need to be statically registered
- pipeline definition syntax could be streamlined (e.g. by getting rid of the `instance` global variable)