Change return value of Schema::childNodes

I'll need to use this method to generate what can be parsed as paths in
the upcoming path parser rework. As a side effect, path completion
generation gets a little bit simpler, because now I don't have to parse
the strings of format "[module:]node" and just trust whatever the schema
gives me.

Change-Id: I881cdbbd8254b846c21cee1ac0a3b7af1e40a696
diff --git a/src/static_schema.hpp b/src/static_schema.hpp
index 43f7b8d..67bd7b9 100644
--- a/src/static_schema.hpp
+++ b/src/static_schema.hpp
@@ -57,7 +57,7 @@
     yang::TypeInfo leafType(const std::string& path) const override;
     std::optional<std::string> leafTypeName(const std::string& path) const override;
     std::string leafrefPath(const std::string& leafrefPath) const override;
-    std::set<std::string> availableNodes(const boost::variant<dataPath_, schemaPath_, module_>& path, const Recursion recursion) const override;
+    std::set<ModuleNodePair> availableNodes(const boost::variant<dataPath_, schemaPath_, module_>& path, const Recursion recursion) const override;
     std::optional<std::string> description(const std::string& path) const override;
     yang::Status status(const std::string& location) const override;