Added scene deletion feature to Scene Selector

- added button to delete a scene (deletes all files except snapshots)

fixes #216 (github)
Added Zip Export Code
Added Export Scene button in Scene Selector

- added Export Scene button in Scene Selector to export scenes to Zip
- refactored Zip export code

fixes #210 (github)
fixes #215 (github)
Added Apache Commons Math in Credits
Updated README
Updated ChangeLog
Added fullscreen mode for Render Preview

fixes #144 (github)
Added help tab in the Render Controls window
Updated README and build script
Print list of available scenes

- when `-render` is used without an argument, Chunky prints available scenes
Fixed hang after headless render failure

- interrupt render workers so that Chunky can be closed by JVM after headless
  render failure

fixes #213 (github)
Added Minecraft download command

fixes #212 (github)
Fall back on downloaded Minecraft Jar
Fixed error causing headless render to never start
Exit with error code on headless/benchmark error
Added unchecked exception handling in main
Launcher passes through Chunky exit code
Wait for Chunky process to exit in headless

- extended wait period for error detection when launching GUI Chunky
- wait for Chunky process to exit when launching headless Chunky

fixes #220 (github)
Include ChangeLog in bundled release notes
Improved logging of texture loading problems