Added explicitly case sensitive/insensitive filter operators.

[geneticdrift]

trafficstars

The default case sensitivity is hard coded for each command. These operators allow to override this default case sensitivity.

[geneticdrift]

Related to #2062 and #494

[MaxKellermann]

This is probably a good idea, but the code doesn't look so good.

• tryParseStringFilter() (badly named, shouldn't start with lower case) allocates memory for no reason
• ParseStringFilter() is being refactored AND new code is being added in one single commit; this makes understanding your code very hard because I can't see what is really being changed
• every ParseStringFilter() call allocates memory on the stack for the std::array and initializes it for no reason; if you really wanted to refactor the function to use an array, then initalize it statically (static constexpr). But since you mixed refactoring and the new feature, I don't understand why you need this array at all
• don't concatenate std::string; this will create many unnecessary allocations. If you really want to format exception messages, use libfmt (e.g. via the FmtRuntimeError() wrapper function)

[MaxKellermann]

The array is still not constexpr, thus it's not guaranteed to initialize at compile time; and the function still allocates heap memory.