Version 4.0.6.0

This version adds support for 1.15 and 1.15.1, and also improves the saved chunks GUI.

• Chunks that were saved after the download was finished (such as those generated or modified after opening the world in singleplayer) are now indicated differently on the saved chunks GUI
• The saved chunks GUI no longer incorrectly hides some chunks that were saved previously after saving chunks near (0, 0) while downloading
• Text on the saved chunks GUI is now located near the top, instead of near the bottom (where the date can get covered by the done button)
• Added support for Minecraft 1.15 (mod-worlddownloader-baseedit-4.0.6.0-mc1.15.0.zip) and 1.15.1 (mod-worlddownloader-baseedit-4.0.6.0-mc1.15.1.zip)
• Partially fixed a crash when opening an inventory that isn't associated with a block (such as plugin-generated enderchests); see #137