Import and export XML with color attributes in hexadecimal representation

[tobiolo]

Due to the autodetection of the representation, std::stoi will convert both the decimal and the hexadecimal representation, thus preserving backwards compatibility.

[tobiolo]

It will not use a leading # as used in web, but 0x. I think it is still a good compromise because the leading 0x leads to the correct detection, it is still more human readable than the decimal representation and using the autodetection enables us to still read the former decimal representation correctly.

[aardappel]

Yup agree that is more elegant :)

[tobiolo]

Thanks for your review and feedback! ☺️