LLDP model added to Tapi

[bzeuner]

LLDP model re-engineered from https://github.com/YangModels/yang/blob/master/standard/ieee/draft/802.1/ieee802-dot1ab-lldp.yang revision 2018-11-11

Additional change: Primitive types MacAddress, Binary and Timeticks added to TapiCommon and then referenced in TapiLldp.

Additional comments:

• TapiOam model not imported yet; so far no augmentation of TAPI classes with LLDP functionality (need discussion)
• Reference stereotype need to be suppressed in the class diagrams (update of style sheet)
• name attribute of Port not modeled (is using localId)
• Type of RemoteStatistics::lastChangeTime not set (depending on TapiOam import)
• ZeroBasedCounter32 and Counter32 modelled as Integer and by using profile properties (bitLength = LENGTH_32_BIT, counter = ZERO_COUNTER/COUNTER)
• Modeling of Binary typed attributes to be discussed
• readOnly attribute property just set to show in diagrams; already defined by property writeAllowed = WRITE_NOT_ALLOWED
• YANG path statements added for information (to be removed finally)
• YANG must statement added for information (to be removed finally)
• Bits-typed data types SystemCapabilitiesMap and TlvsTxEnable have to be updated once TAPI has moved to the latest Profiles.