Let CLI display locally available datasets

[forman]

All CCI data is provided remotely by the ESA ODP. The ECT stores data downloaded from ESA ODP in a cache directory in the user's local file system. Users need a CLI command to identify the locally available datasets so that they can perform operations that won't imply fetching new data from the ESA ODP.

For example, the command

ect ds info --local

would list all locally cached datasets with their temporal coverage.