Merge pull request #55 from alexfikl/deprecation-warnings

experiments/stokes-2d-interior.py

experiments/two-domain-helmholtz.py

pytential/__init__.py

pytential/linalg/proxy.py

pytential/qbx/direct.py

pytential/qbx/fmmlib.py

pytential/qbx/interactions.py

pytential/qbx/refinement.py

pytential/qbx/target_specific/impl.pyx

pytential/symbolic/dof_connection.py

pytential/symbolic/execution.py

pytential/symbolic/matrix.py

pytential/symbolic/primitives.py

pytential/symbolic/stokes.py

test/extra_matrix_data.py

test/test_cost_model.py

test/test_global_qbx.py

test/test_layer_pot_eigenvalues.py

test/test_layer_pot_identity.py

test/test_symbolic.py