Keen Modding Live - Edit level metadata

Today I implemented an API endpoint for Keen Modding live that allows users to change the metadata of levels they own. It supports altering the name, canonical version ID (after checking that the specified version actually belongs to the level), description, and zone ID (again, after verifying that the zone exists). The next step is to add a level properties window to Abiathar Live Studio so that these settings can be changed from the desktop. I should also eventually implement similar functionality on the site.