[Commands] Add #setmana Command. (#1839)

* [Commands] Add #setmana Command.
- Add #setmana [Mana] command to set an NPC or player's mana to a specified amount, or to max if the amount is greater than their max.
- Cleanup #mana command message and logic.

* Update mana.cpp

zone/CMakeLists.txt

@@ -492,6 +492,7 @@ SET(gm_commands
     gm_commands/setgraveyard.cpp
     gm_commands/setlanguage.cpp
     gm_commands/setlsinfo.cpp
+    gm_commands/setmana.cpp
     gm_commands/setpass.cpp
     gm_commands/setpvppoints.cpp
     gm_commands/setskill.cpp