Added water levels to gage height graph

assets/src/scripts/components/hydrograph/drawing-data.js

...ts/src/scripts/components/hydrograph/drawing-data.spec.js

assets/src/scripts/components/hydrograph/index.js

assets/src/scripts/components/hydrograph/legend.js

assets/src/scripts/components/hydrograph/legend.spec.js

...ts/src/scripts/components/hydrograph/time-series-graph.js

...c/scripts/components/hydrograph/time-series-graph.spec.js

assets/src/scripts/selectors/flood-data-selector.js

assets/src/scripts/selectors/flood-data-selector.spec.js

assets/src/scripts/store/flood-inundation.js

assets/src/scripts/web-services/flood-data.spec.js

assets/src/styles/components/hydrograph/_graph.scss