Add latexify.function/expression frontends

[odashi]

Overview

• Add latexify.function and latexify.expression frontend functions.
• Add use_signature option to latexify.get_latex
• Deprecate latexify.with_latex

Details

latexify.function is the same with the old latexify.with_latex, while latexify.expression generates LaTeX without the function's signature:

This behavior is controlled by the difference of the default value of the use_signature option in get_latex.

Also, function and expression would be more intuitive than the old name with_latex to express that the decorator generates a specific form.

References

• Fixes Ability to get latex without getting function name #54

Blocked by

• More and more refactoring. #72

[ShigekiKarita]

LGTM