Added string utility functions to trim, filter and convert.

[paulhoux]

Compared to previous version of the code, I have renamed the in-place versions to *InPlace. They usually perform way better than their copy versions. To prevent issues with the current locale, I have removed calls to std::setlocale and left these for the user. The valueToString functions use std::to_string which performs slightly better than the older ci::toString() function.

[paulhoux]

I am thinking of renaming filter and filterInPlace to removeAnyOf and removeAnyOfInPlace.

Furthermore, it should be possible to rewrite findReplace in such a way that it becomes UTF8 compatible. I could try this code.

[totalgee]

Nice. But how come none of the new valueToString() functions are declared in the Utilities.h file? Also, though Cinder is not yet on C++20, the implementation of these functions should possibly be switched from std::to_string() to std::format() in C++20, which is very fast and particularly good for (by default) printing floating point numbers with just the required precision. (See the examples here.