CLI: Allow key and value encoding to be specified

The CLI allows put operations to specify the encoding of an entry via the --encoding flag, however this only applies to the value and a plain text key must be provided. For example:

put --encoding=application/json --file=example.json example

It should be possible for the key and values encoding to be specified like so:

cache put --key-encoding=application/json --value-encoding=application/json --file=example.json "example"