Portable chests

This mod adds portable variants to the vanilla chests.

Portable chests have the following properties:

• can be carried like normal items
• can be placed and mined
• inventory accessible by right-clicking on them (when in item form)
• can be renamed (but the label will be lost if they're placed)
• can be dropped on the ground (the label stays)
• can contain other portable chests (unlimited storage, but they're not cheap)
• can't be mined or placed by robots

Changelog

0.1.3:

• Fix lost items and chest when mining a portable chest without space in inventory.
  The chest is now spilled as expected.

0.1.2:

• Make sure the steel chest recipe is enabled when loading an existing save
  without the mod and with steel processing already researched.

• Add new builder entities for the place_result of each container item.
  The container entity can't be used because that would allow robots
  to construct using any container item (regardless of their contents).

Also, this avoids a bug where the game will try to build ghosts of
vanilla chests using the portable item rather than vanilla one.

• Remove the "right click to access inventory" mention since the game
  already has one below the description.

0.1.1:

• Fixed "LuaItemStack API call when LuaItemStack was invalid" error

0.1.0:

• Initial release