Simplify muoncoord

• remove setters and instead provide constructor which fully constructs
• remove std::vector of tiles, as a MuonCoord contains either one or two tiles, and two tiles use less space than a single vector, and avoids extra heap allocation -- so use a boost::static_vector with a fixed capacity of two.
• remove explicit 'crossed' data member -- instead, use the # of contained MuonCoords
• adapt code which creates MuonCoords

note: includes !1668 (merged)