Done issue #132, fixes, translation update

- Default directory for the *Open* and *SaveAs* dialogs is user home directory.
Without that, directory is unpredictable, for example when Easypaint is launched from the start menu.
- Warning in case of  problems with opening/saving file
- All dialogs have non-null parent,
to make sure that dialogs are centered over the parent and not auto-positioned.
- Ask canvas size on new image creation (issue #132) 
- Spell correction
- Russian translation update