Update copyright years based on last update date

[AlexDaniel]

In some places it still says “2016”.

[sylints]

What should it say? I'm not too familiar with the topic of Copyright, and looking through the bots I see a mixture of "2016-2017" and "2016".

[AlexDaniel]

@sylints using git you can see history of every file. The dates can simply be updated according to contributions to each file.