brine/visibility and spectator changes

## visibility and spectator changes
If a card is FaceUp, then all players will have visibility of that card.
If a card is FaceDown, then nobody can see the card.
Any player can peek at a facedown card to reveal its identity.  The card will still show as face-down in piles or the table, but the hover preview will show the card's image.  A peek icon appears on the card to show who has seen the card's identity
Piles can set the 'default' visibility for any card within it.  The table is always visibility=Everyone
Piles can add players to the visibility list.  Any player on that list is able to see the contents of that pile.

NEW: A player can add a spectator to the visible players list on a pile.
NEW: The peek icon is added to the pile info panel, showing who has visibility on that pile (similar to cards)
NEW: Remove individual card visibility settings.  Cards are either FaceUp (everyone can see, card's front face is displayed), FaceDown (nobody can see, card identity is kept hidden, card's default back is shown).  Peeking at a card reveals it to that player, revealing its identity but not changing its FaceDown state.

LOGISTICAL ISSUE: OCTGN currently treats Visibility=me as a special case, where the cards are faceup to 'me' but facedown and hidden to everyone else.  This has weird effects on python scripts as a card's FaceUp status isn't consistent between players.
	If a card is FaceUp, then all players will have visibility of that card.
	If a card is FaceDown, then nobody can see the card.
	Any player can peek at a facedown card to reveal its identity. The card will still show as face-down in piles or the table, but the hover preview will show the card's image. A peek icon appears on the card to show who has seen the card's identity
	Piles can set the 'default' visibility for any card within it. The table is always visibility=Everyone
	Piles can add players to the visibility list. Any player on that list is able to see the contents of that pile.

	NEW: A player can add a spectator to the visible players list on a pile.
	NEW: The peek icon is added to the pile info panel, showing who has visibility on that pile (similar to cards)
	NEW: Remove individual card visibility settings. Cards are either FaceUp (everyone can see, card's front face is displayed), FaceDown (nobody can see, card identity is kept hidden, card's default back is shown). Peeking at a card reveals it to that player, revealing its identity but not changing its FaceDown state.

	LOGISTICAL ISSUE: OCTGN currently treats Visibility=me as a special case, where the cards are faceup to 'me' but facedown and hidden to everyone else. This has weird effects on python scripts as a card's FaceUp status isn't consistent between players.