refactor: configuration files for prod must not use "prod" as infix

[ThorstenSuckow]

The default for config files being queried for production should be the package/application name, postfixed with .conf.json instead of .prod.conf.json. This should be done by explicitly checking for the prod-environment. Each other environment should still use the current env-setting as postfix.

[ThorstenSuckow]

If we have any meta information available that clearly defines the current environment as "production", this is doable. Ext.manifest should be investigated therefore. Otherwise, a simple check for the key "prod" does not suffice, since this simply an arbitrary value for the env-property in the coon-js-section in the app.json.