schema:

Moved `Latitude` and `Longitude` types to `nrml_common`.
schema:

Added `CharacteristicSource`.
examples:

Added <characteristicSource> example file, with 1 of each variation:
  - simple fault
  - complex fault
  - multi (planar) surface
examples/source_model/characteristic-source.xml:

Gave some more meaningful names to the <characteristicSource> examples.
examples/source_model/mixed.xml:

Added the 3 variations of <characteristicSources> to the `mixed` example.
_utils:

`deep_eq` now propagates assertion error messages.
tests/tests__utils_test:

Updated usage of `deep_eq` to properly use the new return type.
models:

Minor docstring formatting fixes.
models:

Added CharacteristicSource, PlanarSurface, and Point, for modelling
characteristic sources.
hazard/parsers:

Renamed `_parse_point` method to `_parse_point_source`.
hazard/parsers:

Added support for parsing `<characteristicSource>` types.
tests/hazard/parsers_test:

Updated copyright date.
tests/hazard/parsers_test:

Updated usage of `deep_eq` utility.
tests/hazard/parsers_test:

Expanded existing test to cover the 3 different variations of characteristic
sources.
examples:

Renamed `characteristicSource` element to `characteristicFaultSource`.
hazard/parsers:

Renamed `characteristicSource` to `characteristicFaultSource`.
schema/hazard/source_model/char._source.xsd:

Renamed `characteristicSource` to `characteristicFaultSource`.
examples/source_model:

Planar surfaces of characteristic fault sources must have top/bottom edges
which are completely horizontal.
models:

s/lon/longitude/ and s/lat/latitude/ in `Point`.
hazard/parsers:

s/lon/longitude/ and s/lat/latitude/ to match changes to `models.Point`.