Add support for formatting EffectiveModelContext to organization tree

   module: ietf-netconf-acm
     +--rw nacm
        +--rw enable-nacm?              boolean
        +--rw read-default?             action-type
        +--rw write-default?            action-type
        +--rw exec-default?             action-type
        +--rw enable-external-groups?   boolean
        +--ro denied-operations         yang:zero-based-counter32
        +--ro denied-data-writes        yang:zero-based-counter32
        +--ro denied-notifications      yang:zero-based-counter32
        +--rw groups
        |  +--rw group* [name]
        |     +--rw name         group-name-type
        |     +--rw user-name*   user-name-type
        +--rw rule-list* [name]
           +--rw name     string
           +--rw group*   union
           +--rw rule* [name]
              +--rw name                 string
              +--rw module-name?         union
              +--rw (rule-type)?
              |  +--:(protocol-operation)
              |  |  +--rw rpc-name?            union
              |  +--:(notification)
              |  |  +--rw notification-name?   union
              |  +--:(data-node)
              |     +--rw path                 node-instance-identifier
              +--rw access-operations?   union
              +--rw action               action-type
              +--rw comment?             string