Add extension of parent feature aspect by default

[Matthias Schoettle]

In the default case, every aspect that realizes a sub-feature, will extend an aspect realizing the parent feature. In order to prevent the user forgetting this, by default this extension could be added. I.e., the aspect realizing the closest ancestor in the hierarchy.

[Cécile Camillieri]

Resolves #292: automatically extend aspect realizing parent feature when creating an aspect.

→ <<cset f4d5698e7c38>>