oak-run console should connect to repository in read-only mode by default

With OAK-4182 and OAK-4298, oak-run->console supports connecting to a repository in read only mode. But, as edivad suggested here, it might be more useful to connect to repositories in read-only mode by default and require an explicit read-write flag for write operations.

This, of course, doesn't align with 'always read-write mode' that's operational currently.

Btw, since, 1.5.2 hasn't been release yet, so, we can do this switch pretty cleanly currently. Post 1.5.2 (which would then have --read-only, we might have to retain that flag)