Textboxes in config should be disabled if not relevant

[tmchow]

In config there are text boxes for values that aren't applicable in cases where checkboxes are enabled.

For example:

This is confusing because on first glance, it looks like you need to provide a value (which is defaulted to /tmp).

Instead, if you just set the input box to disabled if that checkbox is checked, then it's more clear what's expected vs not for input. Example: