Enforce single module within an IDL file

[sigiesec]

To simplify generation and the IDL syntax, the IDL syntax should only allow to specify a single module for an IDL file (similar to Java package declarations). Multiple nested modules should be represented using separate IDL files and imports instead.

The new way might look like:

module A.B;

The old way of nested modules like:

module A {
  module B {
  }
}

should then be deprecated and later removed.