Remove more unused things from CryCommon and CrySystem. (#709)

Lots of unrelated removals, I basically tried to remove everything exposed via gEnv that isn't used anymore, and following the threads found a few other things to remove also.

Code/Sandbox/Editor/IEditorImpl.cpp

@@ -66,8 +66,6 @@ AZ_POP_DISABLE_WARNING
 #include "Objects/SelectionGroup.h"
 #include "Objects/ObjectManager.h"
 
-#include "BackgroundTaskManager.h"
-#include "BackgroundScheduleManager.h"
 #include "EditorFileMonitor.h"
 #include "MainStatusBar.h"
 
@@ -176,8 +174,6 @@ CEditorImpl::CEditorImpl()
     regCtx.pCommandManager = m_pCommandManager;
     regCtx.pClassFactory = m_pClassFactory;
     m_pEditorFileMonitor.reset(new CEditorFileMonitor());
-    m_pBackgroundTaskManager.reset(new BackgroundTaskManager::CTaskManager);
-    m_pBackgroundScheduleManager.reset(new BackgroundScheduleManager::CScheduleManager);
     m_pUIEnumsDatabase = new CUIEnumsDatabase;
     m_pDisplaySettings = new CDisplaySettings;
     m_pDisplaySettings->LoadRegistry();
@@ -843,16 +839,6 @@ IIconManager* CEditorImpl::GetIconManager()
     return m_pIconManager;
 }
 
-IBackgroundTaskManager* CEditorImpl::GetBackgroundTaskManager()
-{
-    return m_pBackgroundTaskManager.get();
-}
-
-IBackgroundScheduleManager* CEditorImpl::GetBackgroundScheduleManager()
-{
-    return m_pBackgroundScheduleManager.get();
-}
-
 IEditorFileMonitor* CEditorImpl::GetFileMonitor()
 {
     return m_pEditorFileMonitor.get();