Allow schema for attaching instrumentation methods to include instrumentation method configuration

[delmyers]

Currently, the attach schema for instrumentation methods points to files on disk that contain xml configuration for individual instrumentation methods. While this is convenient for situations in which an instrumentation method may be installed up-front, or attached later, it is cumbersome for situations in which instrumentation methods are attach only.

We have a request to fold the xml schema for instrumentation methods into the schema for attach.