Ability to define backpack radios in config.

tf_hasLRradio = 1;
tf_side = "West";
tf_dialog = "rt1523g_radio_dialog";

This will allow mods to create their own backpack radios with their own interface (procedure to do so will need to be documented).

Unsure if support will be required from plugin side.
Made further improvements to backpack radios, added support for custom function calls for updating dialogs, changed from tf_side to tf_encryptionCode which specifies a variable that contains the encryption code.
Merge pull request #363 from CorruptedHeart/BackPackRadio

Ability to define backpack radios in config.