Improve layout of DLP to allow for more rich descriptions

[kabilar]

Hi team, I would like to make some suggestions regarding the layout of the DLP. Overall I used GitHub's layout for inspiration.

These change would allow for the Description section to be longer and include images, similar to READMEs on GitHub. I added an image to the Description in https://dandiarchive.org/dandiset/001278 and the layout doesn't look that great.

Here are my proposed changes and a preview image is shown below:

1. Create separate tabs for the Dandiset Actions.
2. Make the Overview tab contain two columns.
3. Move the Owners and Versions sections into the right column of the Overview tab.
4. Move the Assets summary, Subject matter, and Keyword section into the right column of the Overview tab.
5. Move the Description section to the left column of the Overview tab.

Perhaps the simplest and first step would be to just move the Description, Subject matter, and Keyword sections into the Overview tab. And by default show the entire contents of the Description (i.e. do not use the + see more button).

Happy to submit a pull request, if the suggestions are agreed upon. Also tagging @bendichter since he has worked on the layout recently.

cc @satra @ayendiki