Migrate netconf-console to Karaf 4 way

Some migration of netconf-console commands has been already done. We
updated commands to use new Karaf shell-related APIs, but we are still
using blueprint XML to create and register these commands.

This does not work with the new API. Avoid using blueprint, use new
available annotations and refactor commands to be more Karaf 4
compliant.

See https://karaf.apache.org/manual/latest/update-notes.html#_commands
for more detail.

JIRA: NETCONF-599
Change-Id: Ib43ecf01e168f77528dadc6a9224dbf70fba4606
Signed-off-by: Jakub Morvay <jmorvay@frinx.io>