Replace WatchLoad

[Katsute]

WatchLoad is inefficient in that while idling, files are not being read. Instead, files should only be changed at the time the file is request (using the last modified time to determine when to update bytes).

This change in WatchLoad could also pave the way for easy implementation of a cache load (#80).

Preload option could expand to have a cache time parameter (instead of creating a new option).

[Katsute]

Replacement of watchload must take into account directory changes (repopulate files and dirs if null).