Add deprecation warnings for features that will disappear with NEST 3.

[heplesser]

NEST 2.12 should issue deprecation warnings for any functions or models that will not be part of NEST 3 and suggest alternatives. Warnings are limited to PyNEST, since few people write SLI these days except for tests.

The critical change in NEST 3 is that subnets will disappear and thus all functions based on subnets. For more on GIDCollections, see #455. Below is a list of model and functions that I suggest to be deprecated.

Models

• subnet: work with GIDCollections instead
• aeif_cond_alpha_RK5: we need to converge on one implementation for this model

PyNEST functions

• BeginSubnet: no longer needed, work with GIDCollections
• EndSubnet: no longer needed, work with GIDCollections
• CurrentSubnet: irrelevant without subnets
• GetChildren: irrelevant without subnets, work with GIDCollections
• GetLID: LIDs disappear with subnets; used index into GIDCollection
• GetLeaves: elements of GIDCollections are leaves
• GetNetwork: irrelevant without subnets, script is responsible for retaining structure information if needed
• GetNodes: you have them in GIDCollections
• LayoutNetwork: use Create(<model>, n=<number>) and get a GIDCollection
• DataConnect: use Connect() with one_to_one rule.

Notes

• PrintNetwork in its current form depends on subnets. I suggest we let it print information from ModelRangeManager instead, i.e., list showing GID ranges and pertaining models.

[Silmathoron]

@heplesser preparing the PR for the correct t_ref implementation in the AEIF models, I just remembered that aeif_cond_alpha_multisynapse is also based on aeif_cond_alpha_RK5... shall we switch it to GSL?

[heplesser]

@Silmathoron Would you have time to do this this week?

[Silmathoron]

Maybe... but I've got the NESTML workshop so probably more like this week-end