drop or mark 'discouraged' CWEs

[raboof]

The autocomplete currently suggests all CWEs, including Discouraged ones.

[raboof]

I don't think we want to drop all discouraged CWEs, as that'd forbid CWE-20 while there's often not an accurate more specific child available.

I guess best would be to show the mapping note information and child CWEs when someone selects a discouraged CWE. Not sure how easy it'd be to integrate that into jsoneditor though.