Intermediate commit

The following classes are moved from org.luwrain.core to org.luwrain.controls:
- EditArea;
- MultilinedEdit;
- MultilinedEditModel;
- SingleLineEdit;
- SingleLineEditModel;
- TreeArea;
- TreeModel.

Other changes:
- org.luwrain.core.popups package is moved to org.luwrain.popups.
Intermediate commit:
- Classes PopupClosing and PopupClosingRequest are added;
- Compilation error fixes.