Feature: Auto-reload from local file

[JeroenvdV]

Updates the 'Load from file' functionality to auto-reload the file contents if the file is changed on the local machine. It stops updating when other changes are made within the interface. Note that this isn't supported yet by all browsers, so the existing method is kept as a fallback.

Limitations:

• Currently the auto-reload functionality is not optional and always on.
• There is no single event that catches changes to the value of the textarea from both user actions and programmatically changing the value, so we rely on a dirty boolean which needs to be set manually whenever the value is updated in the program. This could be prone to future bugs.