Properly identify withheld values in BEA self-employment data

[shawnbot]

Expected behavior

We should have null values in our self-employment YAML files so that we can correctly identify them as withheld, per BEA's descriptions:

(D) Not shown to avoid disclosure of confidential information, but the estimates for this item
    are included in the total.
(L) Less than 10 jobs, but the estimates for this item are included in the total.

Actual behavior

We're parsing BEA's (D) and (L) values as zero, as mentioned in this comment.

This is kind of tricky to debug, because in order to get the self-employment counts we're subtracting the number of wage and salary "mining" (NAICS code 21) jobs from the total number of mining jobs. That happens in our get-bea-data.js script, and I've confirmed that it's producing some of the right numbers by spot-checking the values on the BEA site.

I think that the fix, though, is to treat the self-employment number as withheld if either the total or wage and salary values is listed as (D) or (L). What do you think, @meiqimichelle?

We'll know we're done when...

• Delaware should have just 165 (181 - 16) jobs in 2006, something representing the 177 - L value (where L means "less [sic] than 10 jobs") in 2009, and withheld values instead of zero for 2008-2014. Note: Delaware in 2007 is the only instance of the L, so we might be able to get away with just subtracting 10 from 177 and calling it a day.
• Main should have withheld values in 2008, 2009, and 2012.
• Rhode Island should have withheld values in 2010, 2011, 2013, and 2014.
• DC should have values for all years, because it has non-zero values for all employment and all zeroes for wage and salary jobs.

[coreycaitlin]

Let's try to address this along with #2587

[jennmalcolm]

Through content strategy #2799, we have determined we will not maintain this data in the future. So, I'm closing this issue.