[Lazarus] Using BGRABitmap as TAChart back-end

[Alexander Klenin]

Since there seems to be no support for alpha-channel in LCL,
I plan to implement series transparency by using BGRABitmap compoment.

To avoid requiring non-core package to install TAChart,
it will be added without explicit dependency, similar to the way
AggPas and OpenGL backends are implemented now.

However, this is clearly not the optimal solution,
so does anybody have better ideas?

-- 
Alexander S. Klenin