Notes field for ACS data sources

[jeancochrane]

Create a Notes field for ACS data sources and add views allowing users to create and edit the field. These notes should provide background information about the source of ACS data, and should automatically display on charts that display ACS data from that source.

[beamalsky]

If the site is locking users into a certain way of importing ACS data, I wonder if makes more sense to not let users edit this field. We wouldn't want them to accidentally change it to describe the import incorrectly!