Preprocessor: fix crash when mean or stderr of an estimated parameter is specified as an expression instead of a plain value (bug introduced in 28d30d9a)

C++ Estimation DLL: Adding 1st cut draft RandomWalkMetropolisHastings.cc and related untested files for review

Bugfix: when displaying decision rules, no longer crash if an EXPECTATION operator (in the past) appears as a state variable. Instead, display a (relatively uninformative) line.

This reverts commit 524e9a9c.

lagged endo/exo so that they contain the type-specific symbol ID (instead of
the preprocessor internal symbol ID)

Estimation C++ DLL: Enhancing KalmanFilter performance using symmetric matrix and vector BLAS routines calls  added or enhanced in BlasBindings.hh and dynblas.h + some minor fixes to Matrix.hh and LogPriorDensity.cc

for the jumping distribution).