Avoid printing dot when copyright holder already ends with dot

[FrostyX]

When you set copyright = "My Company, Inc." in conf.py for your documentation and generate html from it, the copyright is rendered like this:

© Copyright 2018, My Company, Inc..

Which is bad, we ideally want to have only one dot at the end.

It can't be workarounded by setting copyright = "My Company, Inc", because then man pages get rendered wrong, e.g.

AUTHOR
       My Company, Inc.

COPYRIGHT
       2018, My Company, Inc

Therefore I am proposing this pull request. It is quite hard to fix it properly because it needs to be done per-theme and therefore it can bring some inconsistencies. If there is a better way to fix it, please let me know.

[Blendify]

I would rather we remove the second added period and leave it up to the author how the copyright is punctuated.

[FrostyX]

@Blendify thank you for the reply. Do you like this solution better?
(Let me know before merging, I will rebase and squash the commits)

[Blendify]

I like this plan better. +1

[FrostyX]

Alright @Blendify, I've rebased the PR.

[Blendify]

Ok, looking for one more quick approval.

[jessetan]

I'd like it even better if the user could customize the entire copyright message (including copyright sign), but that is more the responsibility of Sphinx.

LGTM