Addressing the stone tools bottleneck

So, it's been awhile, but I'm doing my best to make time for hobbies again, so... here's the 0.1.1 version!

This is a minor update that introduces the copper miner who uses bronze pickaxes rather than stone tools. This means once you unlock bronze tools, you can mine more copper without needing more stone tools. This will of course require careful balancing against the other ways you will need bronze tools, but I believe in you.

This update also removes the outdated text on the Windows "are you sure you want to quit?" dialog that claimed the game would not save your progress -- that was not true in 0.1.0 either, so now the game causes less unnecessary panic :)