Alpha 15 release-535

Alpha 15 is almost ready! Here is one last feature for you all to test on the Steam Unstable branch before we call this release baked:

Introducing the Trader’s Stall!
Got a few too many things in your inventory? Have a high level carpenter craft a trader’s stall! Place the stall in the world and interact with it to call a trader to your town. When the trader arrives, click on them, or on the stall, to open a shop window. Profit! Though the trader will leave after a little while (places to go, people to see) you will be able to call a new trader after some time has passed in the game.

This build also fixes a few save/load bugs.

Many thanks to Linda for the trader, and Yang for continued Save/Load compatibility (with Alpha 14!!!!).