Create cider-doc-map and add "\C" versions of the keys when it makes sense.

Very nice initiative to create a doc map. Thanks. 

This patch adds a couple of control prefixed keys. For my brain <kbd>C-c C-d C-d</kbd> is much more convenient than <kbd>C-c C-d d</kbd>.
Please, remove this. There's little value in such wrappers installing this small package will force the huge `helm` package upon the users. Until helm is made more modular (core package without sources) I'd rather not deal with it.