Export existing feature where it is currently, not necessarily in modules/custom

Problem/Motivation

While working on various projects type, Features can be used to package configuration that's not necessarily going to modules/custom.
Currently, Features do not take in consideration the fact that the exported feature is already enabled and is located elsewhere. As it was the default behavior of the 7.x version, I mark it as a regression.

Proposed resolution

Use the feature's current location as base folder of the export.

Remaining tasks

Discuss, Fix, Commit

User interface changes

None.

API changes

None.

Data model changes

None.