improve CYME reader and DSS writer

[NLaws]

working through a CYME v9 conversion to openDSS I have come across a few issues.

openDSS Writer:

• kvarlimit is now kvarmax in openDSS
• replace special characters in object names with "_" (o.w. openDSS will not read the commands correctly)

CYME Reader:

• more informative warnings when load P,Q fail to parse
• handle (not error) negative and zero power factor for loads
• improve doc strings
• improve warning and debug messages
• handle LoadModelID (was adding up multiple LoadModelIDs when it should only use one)

Other

• fix check_transformer_phase_path for case of missing "wires" key
• fix impossible log message in DiTToHasTraits (was trying to log objects)

[kdheepak]

Thanks for making a PR!

[nlaws-camus]

@kdheepak a bunch of openDSS reader tests are failing on NREL/master branch:

tests/readers/opendss/Capacitors/test_capacitor_connectivity.py::test_capacitor_connectivity FAILED                                   [ 81%]
tests/readers/opendss/Capacitors/test_capacitor_kvar.py::test_capacitor_kvar PASSED                                                   [ 81%]
tests/readers/opendss/Lines/test_fuses.py::test_fuses FAILED                                                                          [ 82%]
tests/readers/opendss/Lines/test_line_connectivity.py::test_line_connectivity FAILED                                                  [ 82%]
tests/readers/opendss/Lines/test_line_length.py::test_line_length FAILED                                                              [ 83%]
tests/readers/opendss/Lines/test_linecodes.py::test_linecodes FAILED                                                                  [ 84%]
tests/readers/opendss/Lines/test_linegeometries.py::test_linegeometries XFAIL (This test fails when opendssdirect v0.5.0 is used.)    [ 84%]
tests/readers/opendss/Lines/test_switches.py::test_switches FAILED                                                                    [ 85%]
tests/readers/opendss/Loads/test_load_p_and_q.py::test_load_p_and_q PASSED                                                            [ 85%]
tests/readers/opendss/Loads/test_loads.py::test_loads FAILED                                                                          [ 86%]
tests/readers/opendss/Nodes/test_nodes.py::test_nodes PASSED                                                                          [ 87%]
tests/readers/opendss/Powersource/test_powersource.py::test_powersource FAILED                                                        [ 87%]
tests/readers/opendss/Regulators/test_regulators.py::test_regulators FAILED                                                           [ 88%]
tests/readers/opendss/Transformers/test_transformer_kv.py::test_transformer_kv FAILED                                                 [ 89%]

would you like me to make an issue for this?