All references to `JeffersonLab/rcdb` and `JeffersonLab/ccdb` should be updated to the `code.jlab.org` fork

[c-dilks]

Mostly just the documentation needs updating.

Originally posted by @c-dilks in #90 (comment)

[dglazier]

Thanks Chris.

[c-dilks]

• RCDB is now at https://code.jlab.org/hallb/clas12/rcdb
• CCDB is now at https://code.jlab.org/hallb/clas12/ccdb