Added some functionalities for the pyang plugin:

Summary:
        - the information of the nodes can be changed/extended through
        annotations (opencpe-annotations.yang), see examples
        - the ocpe-actions* files are replaces by the more general
        opencpe-annotations* files
        - specific stuff for mand can be augmented in opencpe-mand.yang
        - yang:date-and-time is now mapped to T_TICKS

Test Plan: build

Reviewers: aschultz

CC: mkraemer, druss

Differential Revision: https://review.tpip.net/D1288
update dm_dmconfig for generated model
Added some functionalities for the pyang plugin:

Summary:
        - the information of the nodes can be changed/extended through
        annotations (opencpe-annotations.yang), see examples
        - the ocpe-actions* files are replaces by the more general
        opencpe-annotations* files
        - specific stuff for mand can be augmented in opencpe-mand.yang
        - yang:date-and-time is now mapped to T_TICKS

Test Plan: build

Reviewers: skattelmann

CC: mkraemer, druss

Differential Revision: https://review.tpip.net/D1288