(core): header includes are not properly sorted

Summary

The header includes sort relies on the Sight < 21 source tree, i.e. the split in src/ and include/ to find the name of the current target. Thus the algorithm fails today to find it and does not sort includes.

Steps to reproduce

Run sheldon on a single file in a sight clone where src/ and include/ is not present (people often have a src folder...). You should observe the following log:

* [Sheldon] Beautifier phase :
* [Sheldon] Using uncrustify: /home/fbridault/software/uncrustify/bin/uncrustify
* [Warning] Failed to find current library for file /home/fbridault/dev/sight/modules/viz/scene3d/SFoo.cpp, includes order might be wrong.
 *
*** [ERROR] Include headers are not correctly sorted in file : /home/fbridault/dev/sight/modules/viz/scene3d/SFoo.cpp. ***

Possible fixes

Adapt the code to the new file tree.