Intermediate commit. More changes will follow: The device selection
logic needs to be moved, too. (And cleaned up.) Instead of the
separate formulacalculationoptions dialog we should simply have a
normal options page for those OpenCL-related settings that will remain
purely Calc-specific, like the formula opcode subsetting.

Change-Id: Id60d95e80d377cbbf5780beb473b221bce06b5e5