@ Gemcutting window: Add number of existing gems of the same type

Reason:
- Gems in use already get greyed out (to prevent creating new ones needlessly, I presume), however, there is nothing to inform us if we already have that gem in the inventory or in the stash.

Suggestion in image: https://imgur.com/a/b0HMJCv

Added suggestion: If player holds alt to see details and mouse-over the feature: show list of gem instances with location and level, like:
- lvl2 gem (inventory)
- lvl51 gem (stash:tabName)
- lvl80 gem (stash:tabName2)

Added suggestion: Allow us to see the gemcutting window WITH inventory and/or stash