JS: Introuce Icinga.History.replaceCurrentState()

Before, we only had pushCurrentState() to add a new URL to the history
stack. But some actions, e.g. "load more" in history views require to
replace the current state instead of pushing. This is what
replaceCurrentState() supports now.

public/js/icinga/history.js

@@ -114,6 +114,26 @@
             }
         },
 
+        /**
+         * Replace the current history entry with the current state
+         */
+        replaceCurrentState: function () {
+            if (! this.enabled) {
+                return;
+            }
+
+            var state = this.getCurrentState();
+
+            if (state.url) {
+                this.icinga.logger.debug('Replacing current history state');
+                window.history.replaceState(
+                    this.getBehaviorState(),
+                    null,
+                    state.url
+                );
+            }
+        },
+
         /**
          * Push the given url as the new history state, unless the history is disabled
          *