Feature request: randomized inventory

[lahm86]

The availability of modifying the start inventory (see resolution to #216) opens up some new options. Some initial ideas are:

• Changing the unarmed/ammoless level options with another option to simply randomize the inventory entirely on each level. There could be various degrees of difficulty to determine what to provide.
• Removing The Seraph from the inventory in Barkhang and make it a pickup to find.
• Night-mode difficulty - clearing the inventory to remove flares, or adding additional flares on "easy" mode.