Allow setting `isActive` default value.

[larryonoff]

TinyConstraints sets isActive default value for all functions to true. So as result all constraints are activated as soon as they created. But this's not efficient according apple documentation, see https://developer.apple.com/documentation/uikit/nslayoutconstraint/1526955-activate

Typically, using this method is more efficient than activating each constraint individually.

So I propose extending the library with something like

public enum TinyConstraintsConfiguration {
  public static var isActiveDefault: Bool = true
}

func anyTinyconstraintsFunction(..., isActive: Bool = TinyConstraintsConfiguration. isActiveDefault) -> Constraint

This should not be source breaking change.