LSS Zone 1.2.0 alpha 4

- contour tracing main logic complete (including openings tracing)
- internal point mark componend added
- layer for internal point mark added
- 'Settings' dialog added (it contains settings for contour tracing for
now only)
- 'Floors count' setting removed from 'room' zone type in zone tool
dialog (it appeared after first launch of a dialog)