Change size of the grid according to the width and height of the screen
Implement exporting car settings to XML

The following features are added:
* Show cars that are currently in the list when opening car editor
* Reset car settings when starts/ends are modified
Use appropriate path when generating XML and PNG files

/Levels/Lv{NUM}/map/lv{NUM}.(xml|png) are generated. Environment variable
VERILOG_TOWN_DEVELOPMENT must be set when developing in order to have the
files generated in the appropriate path.
Fix formatting and unused imports
Rename variable ce to carEditor for clarity
Rename and separate the content of exportXML() method

It is renamed to exportLevel() and is separated to exportXML() and
exportMapImage().
Move multiple try-catch clauses into one try-catch

This change is made to improve readability.
Update JavaDoc, author name, remove TODO, and fix a typo