= Properties Idea =
Properties give solution to the sequence of problems:
 * Initialization order problems
 * Dependency/updating
 * Undo/Redo
 * Save/Load
 * Optimization (central point)
 * Safety (detect errors)
= Properties Kinds =
 * Property
  * !ObjectProperty
   * !FinalProperty
   * !AutoProperty
   * !ResourceProperty
   * !ValueProperty
    * !ParentProperty
    * !UndoProperty - holds an undo manager. If the bean does not have such property, the properties try to locate UndoManager up (to parent). 
  * !ListProperty
   * !ChildrenProperty 

= How to apply properties to Sophie 2.0 =
 * To get rid of the fields, except for immutable classes, and public static final things.
  * Note that final instance fields are not so safe, because they are initialized after the super constructors.
 * To convert mutable classes to !ProObjects
 * To gather more requirements to the properties library and apply them
 * To keep the properties library with high quality, because everything else will depend on it.
 * To be careful of cyclic dependencies (like a = b + 1, b = a + 1). No library can solve them.