Track differences between Engine documentation and Moho

Classes
-----
The engine documentation for classes is pretty good right now-- if it's in `/engine/Sim/*` it's generally sim-side only, if it's in `/engine/User/*`, user-side, and `/engine/Core/*` for both. It's not quite perfect though.

**Core**
* ~~moho.IAniManipulator[](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/User/IAniManipulator.lua) (currently named `CManipulator`)~~ [*done*](4047)

**Core**
* [Blueprints](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/Sim/Blueprints/) (currently in Sim)
* ~~moho.EntityCategory[](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/Core/EntityCategory.lua) ([pending creation](4041))~~ *merged*
* ~~[moho.sound_methods](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/Sim/CSound.lua) ([pending transfer from Sim](4041))~~ *merged*

**User**
* moho.discovery_service_methods[](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/User/CDiscoveryService.lua) ([pending creation](4024))

Functions
-----
The engine documentation for functions is all right. They're generally in the right `/engine/Sim.lua`, `/engine/User.lua`, or `/engine/Core.lua` file.

[**Core**](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/Core.lua)
* `AudioSetLanguage` (unmerged)
* `EntityCategoryContains` (unmerged)
* `EntityCategoryFilterDown` (unmerged)
* `GetBlueprint` (unmerged)
* `GetDepositsAroundPoint` (unmerged)
* `GetGameTimeSeconds` (unmerged)
* `GetTimeForProfile` (missing)
* `GetUnitById` (unmerged)
* `HasLocalizedVO` (unmerged)
* `IsAlly` (unmerged)
* `IsEnemy` (unmerged)
* `IsNeutral` (unmerged)
* `LuaDumpBinary` (missing)
* `ParseEntityCategory` (unmerged)
* `Random` (unmerged)
* `SessionIsReplay` (unmerged)
* `SetFocusArmy` (unmerged)
* `_ALERT` (missing)
* `_TRACEBACK` (missing)

[**User**](https://github.com/FAForever/fa/blob/deploy/fafdevelop/engine/User.lua)
* `SoundIsPrepared` ([pending fixing](4024))
* `StartSound` ([pending fixing](4024))
* `StopAllSounds` ([pending fixing](4024))
* `StopSound` ([pending fixing](4024))
* `SyncPlayableRect` ([pending fixing](4024))
* `TeamColorMode` ([pending fixing](4024))
* `ToggleFireState` ([pending fixing](4024))
* `ToggleScriptBit` ([pending fixing](4024))
* `UISelectAndZoomTo` ([pending fixing](4024))
* `UISelectionByCategory` ([pending fixing](4024))
* `UIZoomTo` ([pending fixing](4024))
* `UnProject` ([pending fixing](4024))
* `ValidateIPAddress` ([pending fixing](4024))
* `ValidateUnitsList` ([pending fixing](4024))
* `WorldIsLoading` ([pending fixing](4024))
* `WorldIsPlaying` ([pending fixing](4024))
* `_c_CreateCursor` ([pending fixing](4024))
* `_c_CreateDecal` ([pending fixing](4024))
* `_c_CreatePathDebugger` ([pending fixing](4024))

**Variables**
-----
No documentation at all, which is fine since there's very little here anyway. It's also a little weird since it depends when the Lua state is initialized.

**Sim**
* `__language` (missing)

**Core**
* `__factory_objects` (missing)
* `_LOADED` (missing)

**Core at Launch**
* `__blueprints` (missing)
* `__factory_objects` (missing)
* `_LOADED` (missing)
* `categories` (missing)