Update options of type sequence instead of overwriting them

We have several options of type tuple like ignore_prefixes.
They have default values that are erased by any new tuple defined from the server configuration or the CLI.

Instead, we should update the current list.
A use case is when we add a new ignored suffixe in Drive but not on the server configuration: when we retrieve that server configuration, we are loosing the newly added suffixe to ignore.

One possiblity would be to also update the server configuration, but we do not want that bacause we would need to wait for all customers to update to the good nuxeo-drive addon version and all not customers have the same needs.

The other possibility, which we will take, is to update the list with the new options.