odealab/coralbook: owner

# `coralbook` 0.0.0.9001

* Replaced name `gallery` by `ccsig-gallery`.
* Changed ownership of `ccsig` and `ccsig-gallery` from `ccsig` organization to `odealab`.
* Repositories' structure is now as follows:

* https://github.com/odealab/
    + ccsig/ (  *   ; website at https://odealab.github.io/ccsig)
    + ccsig-gallery/ (source; website at https://odealab.github.io/ccsig-gallery)
    + coralbook/ (source; website at https://bookdown.org/odealab/coralbook)
    + coralbook/ccsig/ (source;  *  )

Note (*): For the ccsig-gallery, the source code and website are the same thing.

* Made code citable with [zenodo](https://zenodo.org/).
* DOI badge will appear on README.md right after this release.
* Removed git repository from ccsig/ to avoid conflicts with git repository of coralbook/.
* Removed useless files.
* Updated links on README.md of odealab/ccsig and odealab/coralbook.

The ccsig-gallery is outside the coralbook repository, so it does not fit in the DOI citation. It makes no sense to have it inside the coral book and outside the coral book in exactly the same way. It must be outside to be a website functional with GitHub pages (what serves the site). That is also why the website of ccsig is also outside the coralbook, but it doesn't matter because the source of ccsig is inside the coralbook. The site is only one index.html file which source is inside the coralbook. But the site of ccsig-gallery is, as far as I understand, identical to its source. This is not a problem because ccsig-gallery "as is" (with some images borrowed from internet) is of little value. It will should become valuable, eventually, if it evolves into the reference collection. That should be developed to be integrated into the book. But it seems that is not going to happen immediately.