Add configuration-change API

Add configuration-change API

If a configuration file path is defined in an environment variable,
use the Linux kernel's inotify feature to define a watcher on that file.
Xapps that subclass RMRXapp can supply a configuration-change handler
that the framework invokes on write events by polling the watcher.
Xapps that subclass Xapp must invoke a method to poll the watcher.

Bump version to 1.3.0

Issue-ID: RIC-425
Signed-off-by: Lott, Christopher (cl778h) <cl778h@att.com>
Change-Id: I070b36bc7e5a9dcd66c08da0304f7bf9e6a794a1