Implement the DeleteAll interface

Implement the xyz.openbmc_project.Collection.DeleteAll
interface to delete all logging entries.

Change-Id: I007dd8408ebb4e30bf3d3a3c431d747248620aa4
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/manager.hpp b/manager.hpp
index 69d9479..0320b0c 100644
--- a/manager.hpp
+++ b/manager.hpp
@@ -49,6 +49,11 @@
      */
     void erase(const std::string& objectPath);
 
+    /**
+     * Erases all entries
+     */
+    void eraseAll();
+
   private:
     /**
      * The callback for an interfaces added signal