Setting signer logic and computing fees.
AC messages for different transfer ownership states.
Declining ownership logic.
Added `CommunityTokensStore.qml` stub.
Removed deprecated property.
Issue #11964
Implement the UI part of Profile/Settings/Showcase:
- Communities/Accounts/Collectibles/Assets tabs
- drag and drop of items between "hidden" and "in showcase" sections
- ability to set individual items' visibility
- persistency (showcase saved across restarts), not exposed yet due to
missing backend API
Closes#9936
Noelia
Michał Cieślak
Khushboo Mehta
Lukáš Tinkl