Unify item creation/deletion in datastore access

All of our implementations are using the same implementation; all of the
smartness is actually in sysrepo or in libyang. As a bonus, this should
make it possible to remove regular leafs as well (backend-wise at
least).

Change-Id: I177cd233b4b699f66475eae735a659b7c8577534
diff --git a/src/netconf_access.hpp b/src/netconf_access.hpp
index 3875911..3f45a27 100644
--- a/src/netconf_access.hpp
+++ b/src/netconf_access.hpp
@@ -35,12 +35,8 @@
     ~NetconfAccess() override;
     Tree getItems(const std::string& path) override;
     void setLeaf(const std::string& path, leaf_data_ value) override;
-    void createPresenceContainer(const std::string& path) override;
-    void deletePresenceContainer(const std::string& path) override;
-    void createListInstance(const std::string& path) override;
-    void deleteListInstance(const std::string& path) override;
-    void createLeafListInstance(const std::string& path) override;
-    void deleteLeafListInstance(const std::string& path) override;
+    void createItem(const std::string& path) override;
+    void deleteItem(const std::string& path) override;
     void moveItem(const std::string& path, std::variant<yang::move::Absolute, yang::move::Relative> move) override;
     void commitChanges() override;
     void discardChanges() override;