Tiled 0.4.2 released

In this release, added stability and functionality of features from 0.4.1 have been made. Search/replace and hexagonal maps are still considered experimental.

• Added a JNLP for WebStart, contributed by Chris Hazen
• Added a simple plugin for the Mappy FMAP format maps
• Added a plugin dialog for information about plugins
• Added plugin target for building bundled plugins
• Removed API usage deprecated by Java 5.0
• Fixed a NullPointerException when loading plugins
• Fixed layer naming on undo (issue #75)