Ref. dynare#1918

Automatically detected by clang-tidy using the performance-faster-string-find
check.

Also add some annotations to remove some false positives.

There remain some boost-related false positives, it’s unclear how to suppress
them.

They were not enclosed within quotes.

Ref. dynare#1875

In particular, use a std::variant to store the values of options. This ensures
that a given option name can have only one value (previously, for a given
option name, it was possible to store several values as long as they were of
different types).

As a consequence, add many [[maybe_unused]] attributes for legitimate
cases (mainly in virtual functions).

In particular, use this feature in many loops which feature a special treatment
for the first iteration, using a boolean variable (replacing iterator
manipulation). By the way, also use std::exchange() to simultaneously test the
value of this variable and update it.

The vectors were previously stored as strings internally, which would not
necessarily contain the commas which are required in JSON (but not in
MATLAB/Octave). The fix consists in internally storing those options as
std::vector.

Closes: #96

Ref. dynare!1866

The Julia code now uses the JSON output for retrieving the information that
previously was in the driver file.

closes dynare#1708

These functions should have been deleted in
946d105c.

Use ReplaceShorterLiterals option to enforce replacement of all strings.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-raw-string-literal.html

The syntax makes clearer the distinction between a function call and an
initialization. Also, it prevents bugs due to implicit type conversions.

Performed using modernize-use-equals-default from clang-tidy.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-equals-default.html

Performed using modernize-use-default-member-init from clang-tidy.

Manual intervention was needed to remove spurious remaining commas.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-default-member-init.html

Performed using modernize-use-auto from clang-tidy.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-auto.html

Performed using modernize-pass-by-value from clang-tidy.

Manual intervention was needed to fix an issue in MacroValue.hh.
Also replace std::move by move, since we import the std namespace.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-pass-by-value.html