More UI Improvements (0.20.0 Alpha)

This update brings more UI changes and improvements.  Most of this won't be visible to an end-user, but the notable changes are as follows:

• There's a new menu item in the Block World menu to export a world map as a PNG image.
• There's a new built-in terminal emulator, which I used to replace the log window, allowing colored log entries.  
  • Warnings and severe errors will show up orange and red, respectively.
  • If the logging level is reduced (via the config file), then other colors will be seen, as well, for configuration and fine detail entries.
  • The info log entries will appear unchanged.
• The plain text log file has been replaced with an HTML log file.  It appears very similar to the new log window, using the same colors for log entries.
  • Due to the way it's formatted, it should still be fairly readable if viewed in a plain text editor.
  • The plain text log can still be enabled though the config file.

Sorry for the long wait between updates.  My life has been rather crazy in the past month.