Confirmed commit support (v1.0)

Version 1.0 of the confirmed commit capability does not include <cancel-commit> operation nor <persist> and <persist-id> parameters.

Minimal implementation needs to read the state of DS before confirmed <commit> is applied
and save it along with the timer (org.opendaylight.netconf.mdsal.connector.ops.Commit).

The state could be saved in memory and later updated in case of follow-up confirmed <commit>.

Revert (triggered by timer, session termination or <cancel-commit> in case of v1.1 capability version)

would work simply create TX using the saved snapshot and submit it.

Confirming <commit> would remove the timer object.

Then usual <commit> logic should be invoked to support the case

when candidate DS was changed between confirmed and confirming commit.