Allow skill_container to also be skills

[ndrwstn]

Enhancement.

Many skills have associated techniques. It would be nice to be able to nest them under their appropriate skill (as a skill_container). I tried to manually edit the .gcs file for this functionality, but when something is set as a skill_container it suppresses the associated skill fields.

[smithkm]

Alternatively this could also be done purely at the UI level. If both a skill and a technique based off of it are present, the technique is shown as a child of the skill.

It provides less flexibility, but it's less work to manage for the user as it all happens automatically.