configuration files saved without formatting values

The configuration file for the core package (and I guess the others packages too) are dumped with the values not formatted according to the metadata of the configuration.

For instance, the file `metadata.json` of the configuration for the `core` package reads:
```
{
"configuration_content" : {
"maintenance_mode" : {
"title" : "Mainteinance mode (NOT YET IMPLEMENTED)",
"type" : "boolean",
"default" : false,
"details" : "Whether the platform is in maintenance mode"
},
. . .
}
}
```

whereas after pushing a new configuration from the browser, this is what the file `configuration.json` looks like:

```
{
"maintenance_mode": "1",
"navbar_title": "Welcome",
"logo_white": "http:\/\/compose.afdaniele.com\/images\/compose-white-logo.svg",
"logo_black": "http:\/\/compose.afdaniele.com\/images\/compose-black-logo.svg",
"admin_contact_email_address": "administrator@example.com",
"cache_enabled": "0",
"guest_default_page": "login",
"user_default_page": "profile",
"supervisor_default_page": "profile",
"administrator_default_page": "profile"
}
```

It is clear that `maintenance_mode` should be formatted to be `true` rather than `1`.