Initial draft of Poldi2DModel

Implementing some core functions for dealing with intensities, time
domain etc.
Poldi2DModel now computes a 2D-spectrum

It requires a peak list and an instrument, which is extracted from an
exisiting workspace.
LoadSINQFile loads count data in reverse direction

For all calculations, the ordering of raw count data needs to be
reversed, so it is reversed during reading. The reversion logic in
PoldiAutoCorrelationCore is removed. For this, the unit tests are
adjusted.
Shared_ptr typedefs for POLDI-objects, constness optimizations

Added typedefs for boost::shared_ptr for PoldiAbstractChopper,
PoldiAbstractDetector and their const equivalents. In addition, methods
that don't change objects have been marked const explicitly, which
improves performance in PoldiAutoCorrelationCore a bit.