* [sqllab] add support for results backends
Long running SQL queries (beyond the scope of a web request) can now use
a k/v store to hold their result sets.
* Addressing comments, fixed js tests
* Fixing mysql has gone away
* Adressing more comments
* Touchups
* In the tab's dropdown menu under SQL editors, copy query link option is
added. A url with copied query will pop up a new editor tab.
* Made changes based on comments
* Move copy query button to right bottom of sql editor box
* Added in Alanna's code for copy url under menu item
* Fixed linting issues
* pull explore actions button group into component
* use button component
* make sure we render all action buttons
* test that embed code is correct
* don't need before each
* generalize modal trigger for use with plain links or icons
