Executions detail page

[James Santucci]

When you click on an execution in the executions page (#368), you should be taken to a /executions/<id> route that shows you the execution's results and lets you download them (if possible).

This issue is to make that page.

It should show:

• basic information about the execution like its name and arguments (?)
• each STAC asset in its results with a download button if we think it's downloadable

For consistent styles and better defaults than my super fancy bespoke styling, use one of elm-ui-framework or style-framework