- no longer use pointers
- use pass-by-value when possible
- use range-for loops when possible

Most cases can be handled in C++11 by std::stoi() and std::stod().

For the macroprocessor ArrayMV<T>::print() method, use template
specialization (instead of a lexical_cast to detect between T=int and
T=string).

The latter accepts a std::string as argument.

- M and MEX files are now under +${MODELNAME}/
- bytecode and C source now under ${MODELNAME}/model/

Those were treated as comments.

Incidentally, fix a similar issue in the Dynare parser (which is much less
problematic, since double quotes are not used in the Dynare language).

Closes DynareTeam/dynare#1621

transform_unary_ops now introduces aux variables/equations for all unary ops specified by UnaryOpNode::createAuxVarForUnaryOpNode()

In the absence of this option, if a var_model statement(s) is present, then aux vars/eqs are created for the same types of unary operators but only for equations specified in the var_model statement

In the absence of both this option and var_model statements, no unary op auxiliary variables are created

diffs continue to be substituted everywhere; for the moment auxiliary variables are created for diffs of expressions. A forthcoming change will allow auxiliary variables created for diffs of expressions to be linked with their lagged expressions as is currently the case for diffs of variables

Only create auxiliary variables for diffs that appear in VAR equations or equations that have pac_expectations in them

Otherwise, substitute the diff (i.e. `diff(x)` -> `x-x(-1)`)

Otherwise boost::tuple overrides std::tuple.