btCapsuleShape margin and AABB

[emamdouh]

Constructor
Margin is not subtracted from m_implicitShapeDimensions in the construcotr, which results in wrong half extents when setMargin or setLocalScaling is called.

getAabb
Another problem with constructing the half extent of the up axis
halfExtents[m_upAxis] = getRadius() + getHalfHeight();
and that is because both the radius and half height have each a margin deducted. So they should be getting a double margin added back, but they get only one margin
halfExtents += btVector3(getMargin(), getMargin(), getMargin());