Make Attacher a formal installation method

Currently we regard it as experimental.
This means at least adding it to tests.

**Programmatic attach:**
Add to documentation that this is not the recommended way to go with application servers. This is more for standalone java apps where user has the control over the Main class.
Also, provide a way to load configuration file from arbitrary paths (#701).

**Remote attach:**
Add to all integration tests- copy into the container and add a command to attach right after app-server/servlet-container startup (#647).