refac membership

Refac membership

closes #155 (closed) as it removes pending membership
closes #156 (closed) (not entirely, the rest will be done in a separate MR on smith wot)
closes #136 (closed) (it does not link instanciable pallets but fixes the test that were added to show the unwanted behavior)

• remove request_membership call
• remove PendingMembership storage item
• remove PendingMembershipsExpireOn storage item
• remove validate_identity call from identity pallet which is redundant with claim_membership of membership pallet
• improves IdtyStatus
• improves RevocationReason and RemovalReason
• split ConfirmPeriod ValidationPeriod AutorevocationPeriod DeletionPeriod
• remove useless IdtyEvent variants
• improves MembershipRemovalReason
• adds CertToUnconfirmed CertToRevoked variants for duniter-wot Error
• split DistanceEvaluationPending DistanceEvaluationNotRequested

This changes the way identity and membership pallet interact.