Add to dashboard from query page

[basilkhan05]

This pull request is in reference to the - add to dashboard from query page in the issue #24.

This PR allows the user to add the queries to multiple dashboards right from the query show page.

• When the user adds the query, this is appended to the end of the dashboard page (with position n+1, where n is the number of current queries on the dashboard)
• When the user removes the query, the query is deleted from the current position
• The dashboard_query positions are reset after removal of queries for each of the dashboards that were modified

Below is a quick video for an overview of the functionality:

Blazer PR | Hide Mastermind if user_class does not exist

Below is the screenshot of the Add to Dashboard modal:

[ACPK]

@basilkhan05 @ankane - I love this and can't wait for it to be in the master branch!

[ankane]

Hey @basilkhan05, thanks for this one as well. Will take a look when I have some time.