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 2401019 by Jamie Dale in Main branch]
#TTP 308411 - Animation Blueprint: Layered blend per bone should have 2 blends by default, and should have ADD PIN button like regular blueprints
[CL 2315863 by Martin Wilson in Main branch]
#proj core
#branch UE4
#summary Rename Trunc, Round, Floor, Ceil to TruncToInt, RoundToInt, FloorToInt, CeilToInt. Added *ToFloat versions. Repeated for FGenericPlatformMath and all derived classes for all platforms wherever applicable. Corrected comment in Fractional and added Frac() which does HLSL-style fractional (x - floor(x)). Checked for compilation on all projects (with cooking levels wherever applicable). Didn't change Fractional to Frac, this will be done in second commit.
#codereview robert.manuszewski
[CL 2064306 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 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]
