Fix issue with failing to pass kernel limit parameter to density estimation constructor.

[ncguilbeault]

This pull request introduces a new property KernelLimit to the PointProcessModelConfiguration and integrates it into various classes and methods across the codebase. The most important changes include adding the KernelLimit property, updating constructors, and modifying methods to utilize this new property.

Key Changes:

Addition of KernelLimit Property:

• src/PointProcessDecoder.Core/Configuration/PointProcessModelConfiguration.cs: Added the KernelLimit property to the PointProcessModelConfiguration class.

Updates to ClusterlessMarkEncoder:

• src/PointProcessDecoder.Core/Encoder/ClusterlessMarkEncoder.cs: Added the kernelLimit parameter to the KernelDensity constructor calls within the ClusterlessMarkEncoder class. [1] [2]
• src/PointProcessDecoder.Core/Encoder/ClusterlessMarkEncoder.cs: Changed _channelEstimates to be a readonly field.

Updates to SortedSpikeEncoder:

• src/PointProcessDecoder.Core/Encoder/SortedSpikeEncoder.cs: Added the kernelLimit parameter to the KernelDensity constructor call within the GetEstimationMethod method.

Updates to PointProcessModel:

• src/PointProcessDecoder.Core/PointProcessModel.cs: Added the KernelLimit parameter to the PointProcessModel constructor and the Save method. [1] [2]