add ability for panel reload button to override browser cache

[joey04]

This was added in uBO 1.15.0. Now the page reload button that appears after dynamic rule changes in the uBO panel can be shift/ctrl clicked to override the browser cache on reload.

I'm not adding this feature to xBA because XUL browsers already have a dedicated hotkey for cache overriding page reloads. For me, this means pressing Ctrl+F5 or Ctrl+Shift+R.

Keep in mind that:

• Cache-overriding reloads should only be needed when a regular page reload renders improperly. In my experience, it's quite rare.
• Clicking the xBA panel reload button already works properly for regular page reloads.

So in the rare event you need a special cache-override reload, use the browser hotkey.