Add in-memory memoization methods to ClassLoader

+ Wigwam\ClassLoader::cacheFetch(&$data)
+ Wigwam\ClassLoader::cacheStore($data, $ttl=NULL)
Add cache preload for console tab completion

Since tab completion is handled in the grandchild thread, caching was
not being effectively handled (items were cached in a child thread that
was subsequently killed). Now we preload the cache so that all children
can access it. Some things aren't cachable that way though.