Bug: reconciliation and cell merging

[demery]

Bug 1:

@lpcoladangelo discovered that reconciliation is more reliable if a recon column is created from a multi-valued cell and then the recon column is split (rather than split the source column and then creating the recon column). This mitigates a problem in OpenRefine 3.5.1, where names in the recon column are not reconciled and no option is available to search for a matching value.

@demery found that in Safari, OpenRefine 3.5.1 still returned unreconciled values without the "Search for a match" button, but the problem did not occur in Chrome.

This change, splitting the "recon" column rather than the source column should be applied to former owner and authors.

Bug 2:

The current method for merging qid-human with qid-organization and instance of-human with instance of-organization doesn't work. We want to grab the first non-blank value, but we're using coalesce which returns the first non-null value; because blank values (the empty string) aren't null, coalesce won't work:

coalesce("", "a value") // => ""

We want a value to be returned. To find non-blank values we need to use if() and isBlank().