fixes based on will zeng's comments

- [x] That links should not be required to have a strength.
- [x] That I can only add one node at a time to the graphview. I'd like to be able to add all nodes with a given attribute or value.

> - could be an extension of DataProvider that enables this type of interface
> - could be there should be an associated frontend component?
> - could be one component with both?

At this point there is no standard for plugin attributes, so it would be hard to create this functionality without first defining the standard. So #52 needs to happen first, IMO.

- [x] ~~I'd like to be able to add/filter certain kinds of links, not just by strength attributes~~
  - #34 
- [x] ~~I'd like to be able to select links themselves and see their attributes and properties~~
  - #50 
- [x] ~~minimap (am working on this)~~
  - #81 
- [x] Other options besides a force directed graph. (perhaps one that fixes a layout immediately)

>   - should provide graphView endpoint that is `setLayout(Layout layout)`
>   - what other d3 layouts make sense?

  - #9 

- [x] improve css
  - #81 
- [x] One view navigation option we have liked is for the view to pan to centre around whatever node you have selected. This would also be great to have as an option.

> - make this a hotkey, maybe replace doubleclick functionality to do this?
#82

- [x] These may be in your new wiki but it sometimes takes me a while to figure out the keyboard shortcuts so it would be great to have these clearly written up somewhere
  - now on a [celestrium wiki page](https://github.com/jdhenke/celestrium/wiki/Hotkeys)
- [x] ~~It should be easy to edit displayed node and link color based on certain attributes~~
  - #34