Add user warning if unsupported entries in Ceres.json

[dje-dev]

Users might make entries (intended for command line) such as pruning=false into Ceres.json not realizing that command-line and Ceres.json entries are not always the same. This can be confusing, at a minimum the documentation should make this clear and Ceres should warn if unsupported entries are found in the Ceres.json file.