Regression test for bugfix in commit #712c00a7

Incorrect source ids were being given to detectors;
targets were then rightly ignoring the generated spikes.

Also: small coding style compliance edits.

fix compiler warnings and tests with ASSERTIONS on

- update modparser external repo to a version that fixes some compiler
  warnings with clang
- fix a handful of compiler warnings for signed-unsigned comparison in
  tests and when ASSERTIONS are on
- comment out EXPECTS(has_contiguous_segments) where they fail in the
  tests so that we can run all the tests with full debug flags

Bugfix: build fail without TBB.

Plus: coding guidelines compliance.

Address code review pre-merge.

* coding convention adherence
* cell_local_index_type -> cell_lid_type
* time-type parameterized spikes and events
* communicator reset() clears events in flight
* communicator uses routine for gid->group index mapping
* event_queue 'Event' types to follow specified convention/concept.

Not sure how this compiled in the other dev environment...
nonetheless, should be fixed.

Turns out this helps when trying to deliver spikes.

* Makes model.hpp part of library interface; genericize
  value, time types.
* Clarify separation of concerns between model and miniapp.
* Model keeps a record of (local) probe ids for sampler
  attachment by caller.

* Merges upstream master
* Completes abstraction of recipe from model from miniapp
* Adds little stream masking utility to ioutil.hpp
* Unit tests for new functionality still absent

* splitting out model abstraction from miniapp
* move to (gid,index) ids for sources, targets
* simplify lid/gid mappings for communicator, cell group etc.

Add macro to help define lexicographic orderings.

reduce verbosity of profiler instrumentation

Merge Sam's work into my fork

* Consistent use of globally defined integer types for
  indices etc. (catypes.hpp) or template type parameters
  across simulator.
* Support unsigned types in tree, cell_tree and friends.
* Use cell_member_type for probe ids (WIP)
* Rejig mechanism lookup structure (simplifies, plays nicely
  with templated index types.)
* Move spike, connection, events out of communcation namespace
  and directory.

* Test comparison by ref-returning member function.
* Add a 'BY_VALUE' version of the macro, that performs
  the comparison via proxy tuples, allowing comparisons
  via a sequence of arbitrary expressions (including
  non-reference returning member functions).

Aims to avoid boilerplate code and copy/paste errors
for the case where a record-like structure should
be totally ordered by the lexicographic ordering
of a particular ordereed sequence of field values.

recipes.cpp to compilable state.

Validation test updates

* Remove vestigial #if 0
* Add missing cstring include, std:: in validate.cpp
* Simpler synapse index logic in fvm_cell.hpp

* -S (--syntype) option passes argument through to
  synapse creation in `make_cell`.

* Give synapse mechanisms helpers
* Describe synapses in `cell` with location and param list
* Align exp2syn parameters with nrn generated test
* Add unit tests for exp2syn functionality

* Clean up validation CMake
* Use configure-time path to validation data by default
* Checks in validation data
* Bring validate_synapses up to date with current source API.
* Allow -p option in validation test to point to validation
  data directory.

* Add a tweaked version of exp2syn.mod that is modparser compatible.
* Add option to simple_synapse.py to choose which syn type to use.
* Compatibility tweak for runinng nrn scripts with nrniv -python

Feature/plotting

* Use `units` consistently in miniapp.cpp
* Describe the special treatment of the metadata key
  `label` in tsplot.