[C] Call WorldSaveEvent on CraftWorld.save(). Fixes BUKKIT-3681

**The Issue:**

When the CraftWorld.save() method is called (natively only through the "save-all" command), the WorldSaveEvent is not called.

**Justification:**

The event is always called when the server saves a world, but when a world is saved manually, it's saved through the org.bukkit.craftbukkit.CraftWorld class and the event isn't called.

**PR Breakdown:**
This PR makes CraftBukkit call a WorldSaveEvent everytime the save() method in the org.bukkit.craftbukkit.CraftWorld class is used.

**Testing Results and Materials:**
I found no duplication of the event implementation. I used this plugin for testing: https://github.com/Pheasn/WorldSaveTracker.
Binary can be found here: http://pheasn.myftp.org/generalbin/tracker.jar

**JIRA Ticket:**
BUKKIT-3681 - https://bukkit.atlassian.net/browse/BUKKIT-3681