Release 3.1.0

The release brings mostly documentation updates, however two significant changes exist:

• Some implementation classes have been made final since they were never meant to be extended. If you did extend these, please contact me so we can find a proper solution for your use case. I assume this is unlikely to affect anyone, so while this is technically a breaking change I only raised the minor version.
• To provide clearer errors when configuring invalid options on sockets some of the validations the kernel interface does have been duplicated to JavaCAN. In case you want to set options not known to JavaCAN, some of the kernel validations change in an incompatible way or if you want to avoid the (minimal) overhead, simply use the new setOptionUnsafe method that will skip the validation.