Merge branch 'objs-folders-fix' into 'master'

obj folders fix

Partial backtrack of changes I made in !174. Apparently removing all the `.gitignore` files from `/objs`'s subfolders removed the only reason Git was keeping the folders alive (Git doesn't care about empty folders as it turns out). So now they have `.gitignore`s again, with a warning in each not to remove them.

See merge request !177