Mandatory ECF membershlp flag at event level

If an on-line league requires mandatory membership (as defined in the set up of that on-line Event before any matches are played) then any player put on the team sheet for the next match must be a member. The validation would stop a non-member being selected for the next match.

If an on-line league does not require ECF membership then any player put on the team sheet for the next match should get a check/warning.

I do not think it is necessary for any checks to occur on a new player being entered into a league. This will allow players to be registered with a team while being in the process of getting their ECF membership number.