Update metadata index in intake catalogs.

[samueljackson92]

This updates the intake catalog descriptions to match how we are now structuring the s3 storage and adding a future option to include different "levels" of data.

To test:

• Run a local server and go to http://localhost:8081/load_data.html and check it looks ok/reads ok
• Run the load_data.ipynb notebook example.

[jameshod5]

Unable to comment on actual file as it's too large, so going analog mode. Just some typos, runs fine for me:
In `load_data.ipynb':

• Just above the 3rd cell: "level1 is a source that reads from about level1 sources, which contain data directly from the tokamak. In future, derived sources will be added at other product levels. " > Change to "In the future, ...."

• Above the 6th cell: "In the next cell we the url of the first shot to remotely open data from the amc diagnostic." > Correct "we the url..."

[samueljackson92]

Thanks @jameshod5 for the quick review. I will update those typos.

[jameshod5]

Are the conflicts the last part of this PR?

[samueljackson92]

Yup. need to fix my conflicts.