Add graph by URL

[obfuscurity]

Instead of requiring users to import from Saved Graphs. For example, a read-only Graphite user with a composed graph but no way to save it. Should be easy enough to add this in the existing accordion form.

[obfuscurity]

This will depend on some UI refactoring of the toolbar. Currently we have the following actions:

[Import Graphs] [New Dashboard] [Add to Dashboard ▼]

I think [New Dashboard] should be merged in as a menu option in the [Add to Dashboard ▼] dropdown. Likewise, this new [Add Graph URL] feature would seem to be an option under [Import Graphs], which should probably evolve into a dropdown as well. Choosing any of these would load the respective dialog in the accordion-group (which, btw, needs to be unified from the current two accordion-groups to a single one).

Proposed toolbar version:

[New Graphs ▼] [Add View to Dashboard ▼]
 Import Saved    Create New
 Paste URL       Existing 1
                 Existing 2

[obfuscurity]

Do not like the way this is turning out. It just feels wrong that dropdown + link == open modal form. I think we'll go back to the original buttons, but with the context change happening inside the modal instead of the trigger button itself.