rewrite logging in console (#788)

- enhance logging throughout the codebase
- all packages at pkg/ should never log
  or perform log.Fatal() instead packages
  should return errors through functions.
- simplified various user, group mapping
  and removed redundant functions.
- deprecate older flags like --tls-certificate
  --tls-key and --tls-ca as we do not use
  them anymore, keep them for backward compatibility
  for some time.

restapi/client-admin.go

@@ -389,7 +389,7 @@ func (ac adminClient) editTierCreds(ctx context.Context, tierName string, creds
 	return ac.client.EditTier(ctx, tierName, creds)
 }
 
-func newMAdminClient(sessionClaims *models.Principal) (*madmin.AdminClient, error) {
+func newAdminClient(sessionClaims *models.Principal) (*madmin.AdminClient, error) {
 	adminClient, err := newAdminFromClaims(sessionClaims)
 	if err != nil {
 		return nil, err