updated SolverBenchmarkMultiRunTest
added ConstFunction to constrained_functions.h

Change-Id: I9cb490070cb107ca0c9d29ac938dca253b9bafe2
fixed ParticleSwarmUpdater

Change-Id: I07ca1708593babc44662765d9cfc78390b43e98a
added documentation for SolverBenchmark

Change-Id: I406cb17d6001b7bf4888332dbc43f5c15684e362
fixed random

Change-Id: I8c1d099585de45f0edce9a5cbbe39d519a70f570