JSON output of vector options

The following options in the estimation instructions:

        geweke_interval = [0.19 0.49],
        raftery_lewis_qrs=[0.025 0.01 0.95],

are translated in modfile.json as

"convergence.geweke.geweke_interval": [0.19 0.49],
"convergence.rafterylewis.qrs": [0.025 0.01 0.95]

In JSON, vector elements must be separated by a comma.

In DynareBison.yy (lines 3687-3688) the option values are declared as vec_value that is a String. This doesn't let Statements.cc OptionsList::writeJsonOutput() enforce the syntax for a vector.

Fixing this issue should also provide for option values being a vector of integers or of parameters defined higher up in the *.modfile