Clean up: remove interpreter.

CMakeLists.txt

include/CMakeLists.txt

include/dynamic-graph/functions.h

include/dynamic-graph/import.h

include/dynamic-graph/interpreter-helper.h

include/dynamic-graph/interpreter.h

include/dynamic-graph/plugin-loader.h

include/dynamic-graph/pool.h

include/dynamic-graph/shell-procedure.h

src/CMakeLists.txt

src/dgraph/import.cpp

src/dgraph/interpreter-helper.cpp

src/dgraph/interpreter.cpp

src/dgraph/plugin-loader.cpp

src/dgraph/pool.cpp

src/shell/functions.cpp

src/traces/tracer.cpp

tests/CMakeLists.txt

tools/CMakeLists.txt

tools/dg-shell-plugin.cmake