[Commands] Add #setendurance Command. (#1841)

- Add #setendurance [Endurance] command to set an NPC or player's endurance to a specified amount, or to max if the amount is greater than their max.
- Cleanup #endurance command message and logic.

zone/CMakeLists.txt

@@ -488,6 +488,7 @@ SET(gm_commands
     gm_commands/setaaxp.cpp
     gm_commands/setanim.cpp
     gm_commands/setcrystals.cpp
+    gm_commands/setendurance.cpp
     gm_commands/setfaction.cpp
     gm_commands/setgraveyard.cpp
     gm_commands/sethp.cpp