Add to dashboard from query window

[alison985]

from upstream: getredash#955

[alison985]

STRs:

1. Open a query.
2. Select a visualization.
3. Click on the + sign to add it to a dashboard.
4. Search for a dashboard name by typing in the text box. The textbox will display search results as a drop-down.
5. Select a dashboard.
6. The query is added to the end of the dashboard upon selection.
7. The modal closes and brings you back to the query page.

[alison985]

PR #184