xcsoarswiftsplash.svg: Renamed to logo.svg
resource.h: Renamed IDB_SWIFT to IDB_LOGO
Math/fixed: fix ceil(), remove bit-wise NOT operator

The constexpr optimisation of ceil() caused severe breakage because
the operation was using a negated operand.
test/test_fixed: add tests for floor() and ceil()
Screen/Window: Added MoveToCenter() method
WidgetDialog: Added code comments
DigitEntry: Removed duplicate padding

The padding was already applied to the digit_size struct.
Dialogs/TimeEntry: Moved FixedWindowWidget to separate file
DataField/Enum: Use lambda function to sort entries
OrderedTask: simplify check in UpdateIdle()