PauseManager moved to Shared (#3288)

* Namespace changes for moving IPauseManager to shared.

* Namespace changes for moving ITimerManager from Timers to Timing.

* Rebase Fixes.

* Update engine submodule to v0.3.8

Content.Client/Instruments/InstrumentMenu.xaml.cs

@@ -17,7 +17,6 @@ using Robust.Shared.Input;
 using Robust.Shared.IoC;
 using Robust.Shared.Localization;
 using Robust.Shared.Maths;
-using Robust.Shared.Timers;
 using Robust.Shared.Timing;
 using Range = Robust.Client.UserInterface.Controls.Range;