Support binding documentation in config files

[mwestphal]

Is your feature request related to a problem? Please describe.
F3D supports configuring bindings in config files, but there is no documentation logic, leading to partial support in the cheatsheet display, especially when using multiple commands.

Lets add proper support for documenting user bindings, including support for displaying values.

Suggested Solution

• Add support for generating strings out of options in utils::string_template using options API
• Add anoter method to bindings API to be able that can use this templating mechanism
• Design a json syntax to add documentation and template-based value in user configs
• Recover the doc info in F3DConfigFileTools and use the new bidings API
• Add tests