Provider logging should indicate message directionality

[111pontes]

For providers that exchange messages, the directionality of those messages should be indicated (i.e. sent vs. received). While it can be inferred based on protocol knowledge, we can't assume that most users will have such expertise. Currently, YDK-Py logging for NETCONF provider looks like this:

2017-02-21 21:35:00,680 - ydk.services.crud_service - INFO - CREATE operation initiated
2017-02-21 21:35:00,682 - ydk.providers._provider_plugin - DEBUG –
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="urn:uuid:d987d962-9374-4815-b335-ea6b8a62f2af">
  <edit-config>
    <target>
      <candidate/>
    </target>
    <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
      <mpls-ldp xmlns="http://cisco.com/ns/yang/Cisco-IOS-XR-mpls-ldp-cfg">
        <default-vrf>
          <interfaces>
            <interface>
              <interface-name>GigabitEthernet0/0/0/0</interface-name>
              <enable></enable>
            </interface>
            <interface>
              <interface-name>GigabitEthernet0/0/0/1</interface-name>
              <enable></enable>
            </interface>
          </interfaces>
        </default-vrf>
        <enable></enable>
      </mpls-ldp>
    </config>
  </edit-config>
</rpc>

2017-02-21 21:35:00,947 - ydk.providers._provider_plugin - DEBUG –
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="urn:uuid:d987d962-9374-4815-b335-ea6b8a62f2af">
  <ok/>
</rpc-reply>

2017-02-21 21:35:00,948 - ydk.providers._provider_plugin - DEBUG –
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <commit/>
</rpc>

2017-02-21 21:35:01,615 - ydk.providers._provider_plugin - DEBUG –
<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="urn:uuid:d987d962-9374-4815-b335-ea6b8a62f2af">
  <ok/>
</rpc-reply>

[ghost]

Fixed in ydk-cpp code. Will appear in ydk-py once the porting is done