Implement selfDesctruct in the WebSite SC

[pivilartisant]

Implement a self destruct function in the website SC. This should allow users to completely remove their SC from deployment and by extension remove it from the indexer list.

See function below.

Changes should also be propagated to:

• cli add new Self_Destruct function
• ui -> unclear what to do ? should be followed up
• docs -> explain self destruct, differences with delete

More:

• we should also think about adding a command in the cli that will allow users to upgrade their deployed smart contracts

[pivilartisant]

Function should look something like this:

  onlyowner();
  if( !website_empty() ) {
      raise "website not empty, please clear all files first";
      // this check ensures that the self destruct function won't take an infinite amount of gas and fail if there are 10000000 files to delete
  }
  owner = get_owner();
  // TODO delete the Owner datastore entry
  // TODO delete all website-level metadata
  if storage.has("DEWEB_VERSION") {
    storage.del("DEWEB_VERSION");
  }
  set_bytecode("")
  if(owner != "") {
     transfer_coins(get_balance(), owner);
  }
}