License update in files.

Added COPYING file with gplv3 license
Trade is working

Indent corrected for some classes.
Updated file structure.

Udated commands: deleted rsset variants, updated rsset command with three different usages (rsset prices, rsset store, rsset chests).  Deleted rsstores, added rsstore for managing the creation of new stores and entrances.
Updated help files for new commands (not completed).
Updated plugin.yml according to new commands.
Added realshopping.rsset.admin permission node.
TODO: rewrite permission nodes.