Enable setting target nodes to traffic generator

[Naphann]

Add functionality to set target nodes to application for traffic generator.

Example usecase

In .ini files, one can add

*.EndNode1.app.has_specific_recipients = true;
*.EndNode1.app.possible_recipients = [1, 2, 3]; // needs to be valid addresses inside the network

If app.has_specific_recipients is set to false. The behaviour of traffic generator will revert back to selecting a random node in the network as receiver.

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This change is 

[zigen]

Reviewed 3 of 5 files at r1, all commit messages.
Reviewable status: 3 of 5 files reviewed, 1 unresolved discussion (waiting on @Naphann)

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quisp/modules/Application/Application.cc line 125 at r1 (raw file):

    // set self weight to 0; so we don't create self traffic
    temp_end_node_weight_map[my_address] = 0;
    end_node_weight_map = std::ref(temp_end_node_weight_map);

Why do we need this std::ref?
The instance is a local variable, and the end_node_weight_map is a member,
so if we access end_node_weight_map in other methods, is that safe?

[zigen]

Reviewed 2 of 5 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @Naphann)

[Naphann]

Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @zigen)

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quisp/modules/Application/Application.cc line 125 at r1 (raw file):

Previously, zigen (Kentaro "zigen" Teramoto) wrote…

Why do we need this std::ref?
The instance is a local variable, and the end_node_weight_map is a member,
so if we access end_node_weight_map in other methods, is that safe?

I think I misunderstood what std::ref does. I was meaning to make a swap instead of copying the map.

[zigen]

I confirmed it works with this configuration

**.app.has_specific_recipients = true
**.app.possible_recipients = [1]
**.EndNode2[0].is_initiator = true

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Naphann)

[Naphann]

Thanks for the testing!

Reviewed 4 of 5 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Naphann)