Improve some learning-basics code samples

Following code samples in learning-basics should be improved to be more readable and understandable:

- `destroying-instances` - I suggest to rename this code sample to `destroying-distributed-object`
- `unique-names` - there is missing some description about what is the point of this code samples. Even if code includes just a 3 lines it is quite confusing. Some explanation would be useful.
- `wildcard-configuration` - there is missing some description about what is the point of this code samples. There should be probably mentioned that wildcard is used in xml configuration.