Add caching

[joedf]

Cache icons and possibly menu structures?

[joedf]

Thought on this:

1. Determine if Cache needs to created/updated (if enabled, ini option)
   1. Check if a stahky.cache exists
   2. Check if the cache file is too old. (Default age of 7, Add ini option)
   3. Check if Parent/Root search folder has the same files and folders as in the cache file, don't recurse into subfolders
2. If needed, update cache
   1. Use HotKeyIt/ObjDump (forum topic), if not use JSON format
   2. Cache icons if possible