Update

Bug fixes:
- Fixed 'frozen frame from last game' when starting a new game;
- Fixed huge performance drop after a long flight;
- Number of enemies is now limited in order to reduce performance issues;
- Other non-critical bug fixes.
Renderer updates:
- Tagged roofs is now rendered as a cone/pyramid; OSM tag 'roof:shape' is not used yet, other roof shapes and parameters will be implemented in further updates;
- Road lanes count is now limited to prevent possible errors on the map;
- Vertical position of the bridges is now calculated more precisely.
Common improvements:
- Added auto-pause on Alt+Tab and on any other cases when window loses focus;
- Data downloader is now utilizes libcurl for HTTPS support.
Working on the map editor is now in progress.