revert usage of numeric conversion in parameter retrieval since these can be strings; fixes restart regression tests

better solution for #255: don't have to check whethre design variables occur in template file with every simulation run, just once

first steps towards #250; it remains to find a file format and dump the data to a file of this format

throw error if optimizer expression parser doesn't return successfully or if not whole expression has been parsed

modified:   optimizer/Drivers/pisa-opal/pisa-opal.cpp
modified:   optimizer/Expression/CMakeLists.txt
new file:   optimizer/Expression/NumberOfPeaks.cpp
new file:   optimizer/Expression/NumberOfPeaks.h
modified:   optimizer/Util/PeakReader.cpp
modified:   optimizer/Util/PeakReader.h
modified:   src/Optimize/OptimizeCmd.cpp