Renamed test method
Refactored AbstractProperty Test
Added Leftbrained\StandardClass\Property\AbstractProperty::toDefault()
Added parameter to Leftbrained\StandardClass\Property\AbstractProperty::toDefault()
Renamed Leftbrained\StandardClass\Property\AbstractProperty::{toDefault -> castDefault}()
Set Leftbrained\StandardClass\Property\Mixed as sub-class of Leftbrained\StandardClass\Property\AbstractProperty
Implement Leftbrained\StandardClass\Property\Mixed::castDefault()