Fix/composition/add controller

[jdcpni]

• tests/composition/test_control:
  - added tests in TestControlSpecification
that test for order and redundancy of control specification for nodes and controller

• Composition
  - init:  if controller is specified, call self.add_controller
  - add_controller: 
> now adds control_signals to controller for ones specified
for parameters of Mechanism in its constructor
  > added comments to code
  - add_node:  add control_signals to controller for ones specified
for parameters of Mechanism in its constructor
  - "shadow_inputs" > SHADOW_INPUTS

• UNRESOLVED:
  When a controller is specified to control a Mechanism that is not yet a node in the Composition
  it nevertheless gets activated (in call to controller._activate_projections_for_compositions)
  and can run even if the node is never added

• ModulatoryMechanism
  - _remove_default_modulatory_signal():  added method

• ParameterState
  - _check_for_duplicate_projections:
    > fixed presumed bug:  search for projections in path_afferents rather than mod_afferents

[coveralls]

Coverage increased (+0.04%) to 77.968% when pulling 74d3e08 on fix/composition/add_controller into 5762e2c on devel.

[coveralls]

Coverage increased (+0.05%) to 77.973% when pulling 74d3e08 on fix/composition/add_controller into 5762e2c on devel.

[jvesely]

Here are the test failures from travis and appveyor.
I don't why Jenkins doesn't report them:

=================================== FAILURES ===================================
_______________________________ pydocstyle-check _______________________________
[gw1] linux -- Python 3.6.7 /home/travis/virtualenv/python3.6.7/bin/python
/home/travis/build/PrincetonUniversity/PsyNeuLink/psyneulink/core/components/mechanisms/adaptive/modulatorymechanism.py:1642 in private method `_activate_projections_for_compositions`:
        D300: Use """triple double quotes""" (found '''-quotes)
_______________________________ pydocstyle-check _______________________________
[gw1] linux -- Python 3.6.7 /home/travis/virtualenv/python3.6.7/bin/python
/home/travis/build/PrincetonUniversity/PsyNeuLink/psyneulink/core/components/states/inputstate.py:964 in private method `_check_for_duplicate_projections`:
        D300: Use """triple double quotes""" (found '''-quotes)
_______________________________ pydocstyle-check _______________________________
[gw1] linux -- Python 3.6.7 /home/travis/virtualenv/python3.6.7/bin/python
/home/travis/build/PrincetonUniversity/PsyNeuLink/psyneulink/core/components/states/outputstate.py:1139 in private method `_check_for_duplicate_projections`:
        D300: Use """triple double quotes""" (found '''-quotes)
_______________________________ pydocstyle-check _______________________________
[gw1] linux -- Python 3.6.7 /home/travis/virtualenv/python3.6.7/bin/python
/home/travis/build/PrincetonUniversity/PsyNeuLink/psyneulink/core/components/states/parameterstate.py:645 in private method `_check_for_duplicate_projections`:
        D300: Use """triple double quotes""" (found '''-quotes)