restful: pagination fixes
- Refactors the restful_pagination file. (closes #2102)
- Simplifies link_header method when concatenating links into one string.
- Renames file restful_pagination to pagination. (addresses #1724)
- Improves PEP8 and PEP257. (PR #2087)
Co-authored-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Konstantinos Kostis <konstantinos.kostis@cern.ch>