Create "info" command 

that will output at least `namespace/project` of the project as JSON on the stdout

```
cd projectfolder
mergin info 
> 
{
  namespace: "lutra"
  project: "myproject1"
  server: "public.mergincloud.com"
}
```

the `.mergin` subfolder contains information in file `mergin.json` so maybe just reusing that?
