Looks like there may be an issue with 1.1.5

Failed to call hook 'CmdChangeSkin' on plugin 'BuildingSkins v1.1.5' (NullReferenceException: Object reference not set to an instance of an object) at Oxide.Plugins.BuildingSkins.InitializeLayers (BasePlayer player, System.Boolean update) [0x00530] in <5a28122a06b14214b7bc119b30df31c7>:0
at Oxide.Plugins.BuildingSkins.CmdChangeSkin (Oxide.Core.Libraries.Covalence.IPlayer ipPlayer, System.String command, System.String[] arg) [0x0006a] in <5a28122a06b14214b7bc119b30df31c7>:0
at Oxide.Plugins.BuildingSkins.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x003be] in <5a28122a06b14214b7bc119b30df31c7>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <23ba99f131254889867c71f0bd137b1d>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <157a94ee66ab4a7991faecd1eb84be3b>:0
at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <157a94ee66ab4a7991faecd1eb84be3b>:0

Failed to call hook 'CmdConsoleHandler' on plugin 'BuildingSkins v1.1.5' (NullReferenceException: Object reference not set to an instance of an object) at Oxide.Plugins.BuildingSkins.CmdConsoleHandler (ConsoleSystem+Arg arg) [0x00210] in <5a28122a06b14214b7bc119b30df31c7>:0
at Oxide.Plugins.BuildingSkins.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00390] in <5a28122a06b14214b7bc119b30df31c7>:0
at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <23ba99f131254889867c71f0bd137b1d>:0
at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <157a94ee66ab4a7991faecd1eb84be3b>:0
at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <157a94ee66ab4a7991faecd1eb84be3b>:0

Did you remove the old config (JSON) file before installing the update? If not, remove the JSON from the oxide/config folder and reload the plugin. It should automatically creat a new config file once it is finished reloading and hopefully that should fix this.