Fix bug in reconstruction of connection data structures after disconnect and fix small problems with examples

[heplesser]

This PR contains two parts:

• A critical bug fix including new test to ensure connection data structures are properly rebuilt after disconnect.
• Fixes to some examples and the example runner to ensure they work with current master.

This PR changes the order of structural plasticity and spike delivery: When using compressed spikes, we can only deliver spikes through the same connection setup in which they were gathered.

@terhorstd @jougs I label this one as critical because it must make it into 3.6.

[jhnnsnk]

Thanks!
I have run a structural plasticity example and it gives the same result as with NEST 3.5. The test also works.
I am just wondering if in the simulation_manager.cpp the #pragma's are needed because if I try to run with multiple threads I get the error:
nest.lib.hl_api_exceptions.Structural plasticity can not be used with multiple threads: Structural plasticity can not be used with multiple threads in SLI function EnableStructuralPlasticity: . But this goes beyond the specific changes of this PR.