v19.0.0

BREAKING CHANGE: Major renaming, groups removal.

Changed

• Renamed Registry class to World.
• Changed sets API:
  • Renamed Assign(id) to Add(id).
  • Renamed Unassign(id) to Remove(id).
  • Renamed IsAssigned(id) to Has(id).
  • Renamed Assign(id, data) shortcut to Set(id, data).
  • Add(id) and Remove(id) returns true if the component is added or removed
    and false if it is already present or not there.
• Added assertions for negative arguments in some methods.

Added

• Clone() and CopyTo(other) methods to SparseSet, DataSet<T> and World.

Removed

• Groups.