Added translations for /xp command

eng.ini

@@ -51,6 +51,11 @@ commands.enchant.noItem=The target does not hold an item
 commands.enchant.notFound=There is no such enchantment with ID {%0}
 commands.enchant.success=Enchanting succeeded for {%0}
 commands.enchant.usage=/enchant <player> <enchantment ID> [level]
+commands.xp.failure.widthdrawXp=Cannot give player negative experience points
+commands.experience.success=Gave {%0} experience to {%1}
+commands.experience.success.levels=Gave {%0} experience levels to {%1}
+commands.experience.success.negative.levels=Taken {%0} levels from {%1}
+commands.experience.usage=/xp <experience> [player]
 commands.gamemode.success.other=Set {%1}'s game mode to {%0}
 commands.gamemode.success.self=Set own game mode to {%0}
 commands.gamemode.usage=/gamemode <mode> [player]
@@ -256,6 +261,7 @@ pocketmine.command.difficulty.description=Sets the game difficulty
 pocketmine.command.dumpmemory.description=Dumps diagnostic information about memory usage to disk
 pocketmine.command.effect.description=Adds/Removes effects on players
 pocketmine.command.enchant.description=Adds enchantments on items
+pocketmine.command.experience.description=Adds or removes player experience
 pocketmine.command.error.permission=You don't have permission to use the command: {%commandName}
 pocketmine.command.error.playerNotFound=Cannot find a player matching "{%playerName}"
 pocketmine.command.exception=Unhandled exception executing command '{%0}' in {%1}: {%2}
@@ -396,6 +402,8 @@ pocketmine.permission.command.effect.other=Allows the user to modify effects of
 pocketmine.permission.command.effect.self=Allows the user to modify their own effects
 pocketmine.permission.command.enchant.other=Allows the user to enchant the held items of other players
 pocketmine.permission.command.enchant.self=Allows the user to enchant their own held item
+pocketmine.permission.command.experience.other=Allows the user to add or remove experience of other players
+pocketmine.permission.command.experince.self=Allows the user to add or remove their experience
 pocketmine.permission.command.gamemode.other=Allows the user to change the game mode of other players
 pocketmine.permission.command.gamemode.self=Allows the user to change their own game mode
 pocketmine.permission.command.gc=Allows the user to fire garbage collection tasks