Extension of the Identifier message with an additional type

[DerBaertige]

Description

The extension of the "message Identifier" allows the distinction between different types of the identifier value. Currently, during run-time, there is no possibility to represent a Identifier (which must be global unique) or a reference to a previous defined object.

Additionally, during discussed in the Harmonization Group, about Issue #156 that there should be a possibility to define identifiers, which are not set. In addition, the desire arose, that in LanePairing always both IDs should be initialized, which is solved with the new type value TYPE_UNKNOWN.

The usage MAX(uint64) is no longer required in the future, since it is mapped by the types TYPE_UNKNOWN and TYPE_ERROR. For reasons of backwards compatibility, it can be additionally set at TYPE_UNKNOWN oder TYPE_ERROR.

The Sensor specific tracking IDs, which are used by external sensor models, can be mapped by the "message ExternalIdentifier", Pull Request #465 and are more flexible for fulfilling the individual sensor specifications.

Check the checklist

• My code and comments follow the style guidelines and contributors guidelines of this project.
• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests / travis ci pass locally with my changes.

[yash-shah-asam]

Due to a lack of interest in the topic, we will close this PR.