UETOOL-213 - Minimize Slate FString -> FText conversion (remove SLATE_TEXT_ATTRIBUTE)
This fixes any editor/engine specific code that was passing text to Slate as FString rather than FText.
[CL 2399803 by Jamie Dale in Main branch]
* Moved Slate.h into SlateBasics.h and began shifting less commonly used headers into SlateExtras.h.
* Slate.h now simply includes SlateBasics.h and SlateExtras.h.
* Slate.h includes a deprecated warning now to indicate that SlateBasics.h + specific includes should be used instead.
* Moved dozens of inlined functions using Slate widgets into .cpp files to avoid header dependencies.
* All code samples now include SlateBasics.h and SlateExtras.h so future shifts will not break most those projects, but not trigger the deprecation warning of including Slate.h.
#BUN
[CL 2329610 by Wes Hunt in Main branch]
#TTP 334329 - ANIMATION: Multiple transitions in the same direction between the same two nodes draw on top of each other
[CL 2109548 by Martin Wilson in Main branch]
#TTP 314475 - k2: comment boxes within other comment boxes do not move if the outer most box is moved. Also, if two nested comment boxes are moved, the nodes within move 2x as much as they should (video)
#Branch UE4
#Proj GraphEditor, BehaviourTreeEditor
#Add SNodePanel::SNode::FNodeSet typedef for conveniance and clarity
#Change Changed SNodePanel::MoveTo to take an FNodeSet as an exclusion filter on the moved nodes, once moved nodes are appended into this set.
CodeReview Chris.Wood, Nick.Whiting
[CL 2064255 by Ben Cosh in Main branch]
#proj core
#branch UE4
#summary Removed header groups, removed some redundant includes and replaced with forward declarations. Fixed compilation errors.
[CL 2055361 by Mikolaj Sieluzycki in Main branch]
#proj core
#branch UE4
#summary Removed header groups, removed some redundant includes and replaced with forward declarations. Fixed compilation errors.
[CL 2054304 by Mikolaj Sieluzycki in Main branch]
