Hot reloading interval control for non-asset files in app directory requires improvement

[rpkyle]

Initial hot reloading support was provided in #127, including parameters dev_tools_hot_reload_interval and dev_tools_hot_reload_watch_interval.

The initial implementation of hot reloading did not permit a hot reload on initial update to the app itself, and performed a check based on the last event loop (cycle) end time.

Since fiery defaults to updating every 0.1 seconds, this prevented hot reloads for edits to files in the application root directory, while updating assets did trigger a reload event.

A more robust implementation would track whether a hot reload has been performed at least once, and always set permit_reload = TRUE until one reload event has occurred.

On subsequent cycles, it would then be possible to compare the current cycle (wall) time against the (wall) time of the previous reload event.