Added translations for /xp command (#185)

eng.ini

@@ -113,6 +113,10 @@ commands.whitelist.reloaded=Reloaded the whitelist
 commands.whitelist.remove.success=Removed {%0} from the whitelist
 commands.whitelist.remove.usage=/whitelist remove <player>
 commands.whitelist.usage=/whitelist <on|off|list|add|remove|reload>
+commands.xp.failure.widthdrawXp=Cannot give player negative experience points
+commands.xp.success=Gave {%0} experience to {%1}
+commands.xp.success.levels=Gave {%0} experience levels to {%1}
+commands.xp.success.negative.levels=Taken {%0} levels from {%1}
 death.attack.anvil={%0} was squashed by a falling anvil
 death.attack.arrow.item={%0} was shot by {%1} using {%2}
 death.attack.arrow={%0} was shot by {%1}
@@ -333,6 +337,8 @@ pocketmine.command.version.serverSoftwareName=This server is running {%serverSof
 pocketmine.command.version.serverSoftwareVersion=Server version: {%serverSoftwareVersion} (git hash: {%serverGitHash})
 pocketmine.command.version.usage=/version [plugin name]
 pocketmine.command.whitelist.description=Manages the list of players allowed to use this server
+pocketmine.command.xp.description=Adds or removes player experience
+pocketmine.command.xp.usage=/xp <experience[L]> [player]
 pocketmine.crash.archive=The crash dump has been automatically submitted to the Crash Archive. You can view it on {%0} or use the ID #{%1}.
 pocketmine.crash.create=An unrecoverable error has occurred and the server has crashed. Creating a crash dump
 pocketmine.crash.error=Could not create crash dump: {%0}
@@ -446,6 +452,8 @@ pocketmine.permission.command.whitelist.enable=Allows the user to enable the ser
 pocketmine.permission.command.whitelist.list=Allows the user to list all players on the server whitelist
 pocketmine.permission.command.whitelist.reload=Allows the user to reload the server whitelist
 pocketmine.permission.command.whitelist.remove=Allows the user to remove a player from the server whitelist
+pocketmine.permission.command.xp.other=Allows the user to add or remove experience of other players
+pocketmine.permission.command.xp.self=Allows the user to add or remove their experience
 pocketmine.permission.group.console=Grants all console permissions
 pocketmine.permission.group.operator=Grants all operator permissions
 pocketmine.permission.group.user=Grants all non-sensitive permissions that everyone gets by default