Netconf Device Notification

Netconf Device Notification

Requirement - HTTP client should be able to get Device notification
after subscription.

Implementation:
1. Added a new Device Notification Yang for Rest request which takes
 input of Device mount point path
2. Added a DeviceNotificationListenerAdaptor which is get registered
in Device Notification service (on Mount point)
3. Created a dynamic Rest Notification SSE HTTP rest url (Response of 1st rest
call )
4. Updated Test-tool for Notification

JIRA: NETCONF-745
Change-Id: I9cac35d0a7b0f79382d223ae4ec0ac4a3ce2bae9
Signed-off-by: Nikhil Soni <nikk.sonitech@gmail.com>
Signed-off-by: nikhil.soni.lumina <nikk.sonitech@gmail.com>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>