UI
- added UIErrorDialog, appears on umodel crash when UI was active
- improved UIBitmap - now it can display standard Windows icons (error, exclamation etc)
- UITextEdit: added multiline capability
- UIMultilineListbox (ListView) now stores item indices as LVITEM.lParam (preparing to sorting ListView items, in that case LVITEM.iItem values would be randomized, but lParam should be stable)
- main(): guiShown was moved to GApplication