Previously all the module data was in indexed arrays with matching offsets.
Each scriptmodule folder had an initial index and it was incremented per module.
Many package functions expected an index. Indexes were never unique and could change
depending on added modules etc. We also had to convert between them and module IDs.
Now it's all done by module id. There is a numbered index of all modules found, that
increments which is used in the GUI setup menus. But it's not needed by any packaging functions.
md_idx is dropped and the few modules that used it for install checks etc now use md_id.
all packaging functions use the id.
retropie_packages.sh now accepts the module id only.
