SDPPL Pipeline constructor

 DESCRIPTION
 Pipeline is a sequence of data operations such as feature extraction or
 classifiers. Pipelines are always executed through libPRSD C-based
 library and may be run independently of Matlab in custom applications.
 SDPPL is a low-level constructor. High-level creation of pipelines is
 available through functions such as SDLINEAR or SDPCA training a specific
 algorithm on data.
 Pipelines may be also constructed directly by supplying the algorithm
 parameters trained externally. This is done using functions with SDP_
 prefix such as SDP_NORMAL or SDP_AFFINE.