Synchronization filters that uses a child or parent column are not displayed correctly

[Nicklas Nordborg]

The descriptive text for a synchronization filter that uses a child or parent column as expected.

This was fixed in #2202 ([7774]) but was broken by #2218 when an extra element was added to the column definition syntax ([7481]).

The displayed text is now something like: parent(0). for both parent and child columns.

[Nicklas Nordborg]

In 7878:

Fixes #2229: Synchronization filters that uses a child or parent column are not displayed correctly

[Nicklas Nordborg]

In 7887:

References #2229: Synchronization filters that uses a child or parent column are not displayed correctly

Fixes an issue if the child column is from a rawbioassay. In this case, the "item type" is not a subtype, but a raw data type which means we need to check and handle this differently.

Also added a <missing> tag for indicating things that are missing since the filter was created.