new plugin to add users to a location_us group if they login from a US IP address

[pascal-meunier]

Motivation: file permissions require a group for people in the US. Filling the iplocation table of the network database with a copy of the ip ranges applicable to the us is silly because that's a lot of rows to copy and it creates a management problem to keep the copy up to date. Instead, this plugin uses an SQL query with a join operation.

Three files created under core/plugins/user/us/:

• us.php — on login, queries the ipcountry table in the geo database using INET_ATON(). If countrySHORT == 'US', adds the user to location_us. Logs both the
  match and non-match cases. On account deletion, removes the user from location_us (with is_object() guard).
• us.xml — extension manifest
• language/en-GB/en-GB.plg_user_us.sys.ini — admin UI label

[pascal-meunier]

New commit will remove people from location_us group if they login from elsewhere or if they are in the d1_nation group. The purdue group will supersede the location_us group in the sense that unix ACLs will allow access to people in the purdue group for things that are restricted to people in the US.