WIP: Make each project own a task-manager instance.

doc/release/notes/string-token-api.rst

doc/release/notes/task-manager.rst

smtk/attribute/ValueItemTemplate.h

...n/paraview/appcomponents/pqSMTKOperationHintsBehavior.cxx

smtk/operation/Hints.h

smtk/operation/Hints.xml

smtk/project/Project.cxx

smtk/project/Project.h

smtk/project/Registrar.cxx

smtk/project/json/jsonProject.cxx

smtk/project/operators/Create.sbt

smtk/project/operators/Read.cxx

smtk/project/operators/Read.sbt

smtk/string/Manager.cxx

smtk/string/Manager.h

smtk/string/Token.cxx

smtk/string/Token.h

smtk/string/json/jsonToken.cxx

smtk/task/Instances.cxx

smtk/task/Instances.h