Moved exceptions to package com.sk89q.worldedit to prevent potential collision.

src/WorldEditSession.java

@@ -17,6 +17,8 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
+import com.sk89q.worldedit.*;
+
 /**
  *
  * @author sk89q