Reworked the plugin for better overall performance.

[WildCard65]

This plugin will no longer constantly iterate the game for rockets, instead it'll do a one time iteration for the relevant inventories, creating them prematurely if needed.

[akarnokd]

See #8.

[akarnokd]

After careful consideration, relying on the hidden, and otherwise unused, inventory is risky as it may eventually be removed.

Instead, the idea is to scan for rockets upon start, then hook into the launch button and update the rocket counts right there.