Merge pull request #2785 from metabase/0.18-docs

docs/users-guide/01-what-is-metabase.md

docs/users-guide/02-database-basics.md

docs/users-guide/03-asking-questions.md

docs/users-guide/04-visualizing-results.md

docs/users-guide/05-sharing-answers.md

docs/users-guide/06-dashboard-tips.md

docs/users-guide/06-dashboards.md

docs/users-guide/07-dashboard-filters.md

docs/users-guide/08-multi-series-charting.md

docs/users-guide/09-pulses.md

docs/users-guide/10-metabot.md

docs/users-guide/11-data-model-reference.md

docs/users-guide/images/dashboard-filters/01-add-filter.png

docs/users-guide/images/dashboard-filters/02-filter-type.png

.../users-guide/images/dashboard-filters/03-wiring-cards.png

...users-guide/images/dashboard-filters/04-select-fields.png

docs/users-guide/images/dashboard-filters/05-edit-label.png

...ers-guide/images/dashboard-filters/06-edit-and-remove.png

...users-guide/images/dashboard-filters/07-default-value.png

docs/users-guide/images/dashboard-filters/08-use-filter.png