Added a Select All for the inventory view

Hi, 

I like your extension quite a bit. I had a frequent use case in the inventory panel of wanting to select multiple different categories, so I added a select all button. 

If I can sneak some more coding time in before my gf wakes up and keep working on that page. I would like to add calculated dps fields, and also use the cache you setup on top indexeddb to store what boxes are checked for reloads.

Thanks for your time.