Replaced the algorithm from helper.binomial_coefficient with one that is
much faster for high input numbers.
Moved some of the checks in SplitSignal/SplitSpectrum for out-of-bounds
channel indices from the setter method to the getter method.
New features for the SignalFile/SpectrumFile classes:
 - GetLength and GetSamplingRate/GetResolution methods
 - the capability to read itaAudio files from the ITA-Toolbox
Bugfix: the setup.py file ignored the Matlab script that was needed for
reading itaAudio files.
Make the ChannelData's errormessage for incompatible labels more verbose
Bugfix: SuMPF no longer crashes when reading itaAudio-files with empty or
unicode units or channel names.
FILTER_WITH_COEFFICIENTS option for the FilterGenerator class to specify
a filter by its laplace coefficients.
Bugfix: The SPECTRUM algorithm of the ResampleSignal class changed the
amplitude of the resampled signal.
A flag for the DurationToLength class that forces the calculated length to
be even.
Bugfix: A sweep and silence length that added up to an odd value could
crash the RecordTransferFunction program.
Add a warning that the helper.differentiate function is faulty
Bugfix: Connecting two connectors announces a value change now.
New differentiation functions "differentiate_fft" and "differentiate_spline".
The helper.math.py file is renamed to helper.sumpfmath.py to avoid confusion
with the standard math module when importing.

API change: the helper.differentiate function uses a different algorithm now
The differentiation function for the DifferentiateSignal class is now
selectable.
Improved unittest for proper documentation of the signal processing classes.
Changes to the FilterGenerator class
 - the FilterGenerator only accepts one filter function now
 - the filter function can be set with the constructor
 - new filter functions CONSTANT and DERIVATIVE
 - filter functions can now calculate the transfer function in dependency
   of the output spectrum's length and resolution

API changes: the AddFilter method has been replaced by the SetFilter method
which is no longer a MultiInput. The RemoveFilter and ReplaceFilter methods
have been removed.
The MultiInputData class has a Clear method now.
The MergeSignals and MergeSpectrums classes can now take mergeable data
sets as a constructor argument.
Improvements to the RecordTransferFunction example:
 - bugfix for an error that occured, when the hardware's sampling rate was
   not the same as SuMPF's default sampling rate.
 - bugfix for the wrong labeling of kept measurement data.
 - shorter signal durations during the setup of the signal processing chain
   to speed up the start of the program.
 - the examples.RecordTransferFunction function now imports the main.py
   file, which reduces duplicate code.
Improvements to the ChannelDataProperties class.